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Ioannou, Andrew George. "Applications of time-dependent current density functional theory." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624734.
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Jensen, Daniel S. "Real-Space Approach to Time Dependent Current Density Functional Theory." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2559.
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A real-space time-domain calculation of the frequency-dependent dielectric constant of nonmetallic crystals is outlined and the integrals required for this calculation are computed. The outline is based on time dependent current density functional theory and is partially implemented in the ab initio density functional theory FIREBALL program. The addition of a vector potential to the Hamiltonian of the system is discussed as well as the need to include the current density in addition to the particle density. The derivation of gradient integrals within a localized atomic-like orbital basis is presented for use in constructing the current density. Due to the generality of the derivation we also give the derivation of the kinetic energy, dipole, and overlap interactions.
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Yam, Chi-yung, and 任志勇. "Linear-scaling time-dependent density functional theory." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31246199.
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Cazorla, Julien J. A. "Real time techniques in time-dependent density functional theory." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615790.
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Van, Caillie Carole. "Electronic structure calculations using time-dependent density functional theory." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621205.
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Esplugas, Ricardo Oliveira. "Density functional theory and time-dependent density functional theory studies of copper and silver cation complexes." Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496931.
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A particular emphasis of this thesis has been to provide insight into the underlying stability of these complexes and hence interpret experimental data, and to establish the development of solvation shell structure and its effect on reactivity and excited states. Energy decomposition analysis, fragment analysis and charge analysis has been used throughout to provide deeper insight into the nature of the bonding in these complexes. This has also been used successfully to explain observed preferential stability and dissociative loss products.
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Tempel, David Gabriel. "Time-Dependent Density Functional Theory for Open Quantum Systems and Quantum Computation." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10208.
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First-principles electronic structure theory explains properties of atoms, molecules and solids from underlying physical principles without input from empirical parameters. Time-dependent density functional theory (TDDFT) has emerged as arguably the most widely used first-principles method for describing the time-dependent quantum mechanics of many-electron systems. In this thesis, we will show how the fundamental principles of TDDFT can be extended and applied in two novel directions: The theory of open quantum systems (OQS) and quantum computation (QC). In the first part of this thesis, we prove theorems that establish the foundations of TDDFT for open quantum systems (OQS-TDDFT). OQS-TDDFT allows for a first principles description of non-equilibrium systems, in which the electronic degrees of freedom undergo relaxation and decoherence due to coupling with a thermal environment, such as a vibrational or photon bath. We then discuss properties of functionals in OQS-TDDFT and investigate how these differ from functionals in conventional TDDFT using an exactly solvable model system. Next, we formulate OQS-TDDFT in the linear-response regime, which gives access to environmentally broadened excitation spectra. Lastly, we present a hybrid approach in which TDDFT can be used to construct master equations from first-principles for describing energy transfer in condensed phase systems. In the second part of this thesis, we prove that the theorems of TDDFT can be extended to a class of qubit Hamiltonians that are universal for quantum computation. TDDFT applied to universal Hamiltonians implies that single-qubit expectation values can be used as the basic variables in quantum computation and information theory, rather than wavefunctions. This offers the possibility of simplifying computations by using the principles of TDDFT similar to how it is applied in electronic structure theory. Lastly, we discuss a related result; the computational complexity of TDDFT.Physics
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Zhang, Xing. "Spin-flip time-dependent density functional theory and its applications to photodynamics." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469628877.
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Lacombe, Lionel. "On dynamics beyond time-dependent mean-field theories." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30185/document.
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Cette thèse présente différentes approches quantiques pour l'exploration de processus dynamiques dans des systèmes multiélectroniques, en particulier après une forte excitation qui peut aboutir à des effets dissipatifs. Les théories de champ moyen sont un outil utile à cet égard. Malgré l'existence de nombreux travaux réalisés ces deux dernières décennies, ces théories peinent à reproduire complètement la corrélation à deux corps. La thermalisation est un des effets des collisions électron-électron. Après un chapitre introductif, on présentera dans le chapitre 2 le formalisme de plusieurs méthodes étudiées dans cette thèse, ayant pour but la description de ces effets en ajoutant un terme de collision au champ moyen. Ces méthodes sont appelées Stochastic Time-Dependent Hartree Fock (STDHF), Extended TDHF (ETDHF) et Collisional TDHF (CTDHF). Cette dernière méthode représente d'une certaine façon le résultat principal de cette thèse. L'implémentation numérique de chacune de ces méthodes sera aussi examinée en détail. Dans les chapitres 3, 4 et 5, nous appliquerons à différents systèmes les méthodes présentées dans le chapitre 2. Dans le chapitre 3, nous étudions d'abord un canal de réaction rare, ici la probabilité d'un électron de s'attacher à un petit agrégat d'eau. Un bon accord avec les données expérimentales a été observé. Dans le chapitre 4, un modèle fréquemment utilisé en physique nucléaire est résolu exactement et comparé quantitativement à STDHF. L'évolution temporelle des observables à un corps s'accorde entre les deux méthodes, plus particulièrement en ce qui concerne le comportement thermique. Néanmoins, pour permettre une bonne description de la dynamique, il est nécessaire d'avoir une grande statistique, ce qui peut être un frein à l'utilisation de STDHF sur de larges systèmes. Pour surpasser cette difficulté, dans le chapitre 5 nous testons CTDHF, qui a été introduit dans le chapitre 2, sur un modèle à une dimension (et sans émission électronique). Le modèle se compose d'électrons dans un potentiel de type jellium avec une interaction auto-cohérente sous la forme d'une fonctionnelle de la densité. L'avantage de ce modèle à une dimension est que les calculs STDHF sont possibles numériquement, ce qui permet une comparaison directe aux calculs CTDHF. Dans cette étude de validité du concept, CTDHF s'accorde remarquablement bien avec STDHF. Cela pose les jalons pour une description efficace de la dissipation dans des systèmes réalistes en trois dimensions par CTDHFThis thesis presents various quantal approaches for the exploration of dynamical processes in multielectronic systems, especially after an intense excitation which can possibly lead to dissipative effects. Mean field theories constitute useful tools in that respect. Despite the existence of numerous works during the past two decades, they have strong difficulties to capture full 2-body correlations. Thermalization is one of these effects that stems from electron-electron collisions. After an introductory chapter, we present in Chapter 2 the formalism of the various schemes studied in this thesis toward the description of such an effect by including collisional terms on top of a mean field theory. These schemes are called Stochastic Time-Dependent Hartree Fock (STDHF), Extended TDHF (ETDHF) and Collisional TDHF (CTDHF). The latter scheme constitutes in some sense the main achievement of this thesis. The numerical realizations of each scheme are also discussed in detail. In Chapters 3, 4 and 5, we apply the approaches discussed in Chapter 2 but in various systems. In Chapter 3, we first explore a rare reaction channel, that is the probability of an electron to attach on small water clusters. Good agreement with experimental data is achieved. In Chapter 4, a model widely used in nuclear physics is exactly solved and quantitatively compared to STDHF. The time evolution of 1-body observables agrees well in both schemes, especially what concerns thermal behavior. However, to allow a good description of the dynamics, one is bound to use a large statistics, which can constitute a hindrance of the use of STDHF in larger systems. To overcome this problem, in Chapter 5, we go for a testing of CTDHF developed in Chapter 2 in a one-dimensional system (and without electronic emission). This system consists in electrons in a jellium potential with a simplified self-consistent interaction expressed as a functional of the density. The advantage of this 1D model is that STDHF calculations are numerically manageable and therefore allows a direct comparison with CTDHF calculations. In this proof of concept study, CTDHF compares remarkably well with STDHF. This thus paves the road toward an efficient description of dissipation in realistic 3D systems by CTDHF
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Tafur, Sergio. "NONLINEAR OPTICAL PROPERTIES OF ORGANIC CHROMOPHORES CALCULATED WITHIN TIME DEPENDENT DENSITY FUNCTIONAL THEORY." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4079.
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Time Dependent Density Functional Theory offers a good accuracy/computational cost ratio among different methods used to predict the electronic structure for molecules of practical interest. The Coupled Electronic Oscillator (CEO) formalism was recently shown to accurately predict Nonlinear Optical (NLO) properties of organic chromophores when combined with Time Dependent Density Functional Theory. Unfortunately, CEO does not lend itself easily to interpretation of the structure activity relationships of chromophores. On the other hand, the Sum Over States formalism in combination with semiempirical wavefunction methods has been used in the past for the design of simplified essential states models. These models can be applied to optimization of NLO properties of interest for applications. Unfortunately, TD-DFT can not be combined directly with SOS because state-to-state transition dipoles are not defined in the linear response TD approach. In this work, a second order CEO approach to TD-DFT is simplified so that properties of double excited states and state-to-state transition dipoles may be expressed through the combination of linear response properties. This approach is termed the a posteriori Tamm-Dancoff approximation (ATDA), and validated against high-level wavefunction theory methods. Sum over States (SOS) and related Two-Photon Transition Matrix formalism are then used to predict Two-Photon Absorption (2PA) profiles and anisotropy, as well as Second Harmonic Generation (SHG) properties. Numerical results for several conjugated molecules are in excellent agreement with CEO and finite field calculations, and reproduce experimental measurements well.M.S.
Department of Physics
Sciences
Physics MS
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Craig, Colleen F. "Nonadiabatic molecular dynamics in time-dependent density functional theory with applications to nanoscale materials /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8671.
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Dinh, Phuong Mai. "Time-dependent density functional theory applied to clusters and molecules in contact with an environment." Habilitation à diriger des recherches, Université Paul Sabatier - Toulouse III, 2009. http://tel.archives-ouvertes.fr/tel-00981941.
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We present recent theoretical and methodological explorations on the dynamics of sodium clusters in the framework of Time-Dependent Density Functional Theory (TDDFT), coupled non-adiabatically to Molecular-Dynamics (MD). In particular, a hierarchical approach, in the spirit of Quantum-Mechanical/Molecular-Mechanical methods, has been developed for the description of metal clusters in interaction with a dynamically polarizable substrate, as rare gases or MgO. Numerous examples of application of this approach (Na clusters in or on Ar substrate, Na clusters deposited on MgO; optical response, dynamical deposition, laser irradiation, ...) are reviewed. We also briefly discuss complementing research activities. Formal developments on the Self-Interaction Correction issue in DFT and TDDFT are discussed in a word. We have furthermore extended our TDDFT-MD theory to the case of organic (C, N, O, H made) systems and a few examples of investigated dynamical processes are presented. Recent calculations of photoelectron angular distributions of free metal clusters are reported as well. We finally sketch with some perspectives for the years to come.
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Niesert, Manfred [Verfasser]. "Ab initio calculations of spin-wave excitation spectra from time-dependent density-functional theory / Manfred Niesert." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/102156754X/34.
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Hofmann, Fabian [Verfasser], and Stephan [Akademischer Betreuer] Kümmel. "The Sternheimer Approach to Linear Response Time-Dependent Density Functional Theory / Fabian Hofmann ; Betreuer: Stephan Kümmel." Bayreuth : Universität Bayreuth, 2020. http://d-nb.info/1223982041/34.
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Hofmann-Mees, Dirk [Verfasser], and Stephan [Akademischer Betreuer] Kümmel. "Charge and excitation-energy transfer in time-dependent density functional theory / Dirk Hofmann-Mees. Betreuer: Stephan Kümmel." Bayreuth : Universität Bayreuth, 2013. http://d-nb.info/1059353652/34.
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Drummond, Michael L. "Denisty functional theory investigations of the ground- and excited-state chemistry of dinuclear organometallic carbonyls." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1104284754.
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Jokar, Jeiran Verfasser], Nicole [Akademischer Betreuer] Helbig, and Carsten [Akademischer Betreuer] [Honerkamp. "Adiabatic approximations within time-dependent density functional theory for the non-linear regime / Jeiran Jokar ; Nicole Helbig, Carsten Honerkamp." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1161411771/34.
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Rüger, Robert, Lenthe Erik van, Thomas Heine, and Lucas Visscher. "Tight-binding approximations to time-dependent density functional theory: A fast approach for the calculation of electronically excited states." AIP Publishing, 2016. https://ul.qucosa.de/id/qucosa%3A21501.
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We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB.
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Jokar, Jeiran [Verfasser], Nicole Akademischer Betreuer] Helbig, and Carsten [Akademischer Betreuer] [Honerkamp. "Adiabatic approximations within time-dependent density functional theory for the non-linear regime / Jeiran Jokar ; Nicole Helbig, Carsten Honerkamp." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1161411771/34.
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Zhu, Ying. "A Comparison of Calculation by Real-Time and by Linear-Response Time-Dependent Density Functional Theory in the Regime of Linear Optical Response." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460554444.
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Richard, Ryan M. "Time-Dependent Density-Functional Description of the 1La State in Polycyclic Aromatic Hydrocarbons." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1302098974.
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Wang, Yuekui [Verfasser]. "Application of the Time-Dependent Density Functional Theory to the Study of Chiroptical Properties of Organic and Inorganic Compounds / Yuekui Wang." Aachen : Shaker, 2003. http://d-nb.info/1170543413/34.
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Maier, Toni Mike [Verfasser], Martin [Akademischer Betreuer] Kaupp, Martin [Gutachter] Kaupp, and Thomas [Gutachter] Körzdörfer. "Development of local hybrid functionals for time-dependent density functional theory / Toni Mike Maier ; Gutachter: Martin Kaupp, Thomas Körzdörfer ; Betreuer: Martin Kaupp." Berlin : Technische Universität Berlin, 2016. http://d-nb.info/1156011787/34.
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Bhandari, Srijana. "AN ELECTRONIC STRUCTURE APPROACH TO UNDERSTAND CHARGE TRANSFERAND TRANSPORT IN ORGANIC SEMICONDUCTING MATERIALS." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1606836665551399.
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Falklöf, Olle, and Bo Durbeej. "Modeling of phytochrome absorption spectra." Linköpings universitet, Beräkningsfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-92393.
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Phytochromes constitute one of the six well-characterized families of photosensory proteins in Nature. From the viewpoint of computational modeling, however, phytochromes have been the subject of much fewer studies than most other families of photosensory proteins, which is likely a consequence of relevant high-resolution structural data becoming available only in recent years. In this work, hybrid quantum mechanics/molecular mechanics (QM/MM) methods are used to calculate UV-vis absorption spectra of Deinococcus radiodurans bacteriophytochrome. We investigate how the choice of QM/MM methodology affects the resulting spectra and demonstrate that QM/MM methods can reproduce the experimental absorption maxima of both the Q and Soret bands with an accuracy of about 0.15 eV. Furthermore, we assess how the protein environment influences the intrinsic absorption of the bilin chromophore, with particular focus on the Q band underlying the primary photochemistry of phytochromes.
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Weerawardene, K. L. Dimuthu M. "Optical and luminescence properties of noble metal nanoparticles." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38189.
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Doctor of PhilosophyDepartment of Chemistry
Christine M. Aikens
The remarkable optical and luminescence properties of noble metal nanoparticles (with diameters < 2 nm) attract researchers due to potential applications in biomedicine, photocatalysis, and optoelectronics. Extensive experimental investigations on luminescence properties of thiolate-protected gold and silver nanoclusters during the past decade have failed to unravel their exact photoluminescence mechanism. Herein, density functional and time-dependent density functional theory (DFT and TDDFT) calculations are performed to elucidate electronic-level details of several such systems upon photoexcitation. Multiple excited states are found to be involved in photoemission from Au₂₅(SR)₁₈– nanoclusters, and their energies agree well with experimental emission energies. The Au₁₃ core-based excitations arising due to electrons excited from superatom P orbitals into the lowest two superatom D orbitals are responsible for all of these states. The large Stokes shift is attributed to significant geometrical and electronic structure changes in the excited state. The origin of photoluminescence of Ag₂₅(SR)₁₈– nanoclusters is analogous to their gold counterparts and heteroatom doping of each cluster with silver and gold correspondingly does not affect their luminescence mechanism. Other systems have been examined in this work to determine how widespread these observations are. We observe a very small Stokes shift for Au₃₈(SH)₂₄ that correlates with a relatively rigid structure with small bond length changes in its Au₂₃ core and a large Stokes shift for Au₂₂(SH)₁₈ with a large degree of structural flexibility in its Au₇ core. This suggests a relationship between the Stokes shift of gold−thiolate nanoparticles and their structural flexibility upon photoexcitation. The effect of ligands on the geometric structure and optical properties of the Au₂₀(SR)₁₆ nanocluster is explored. Comparison of the relative stability and optical absorption spectra suggests that this system prefers the [Au₇(Au₈SR₈)(Au₃SR₄)(AuSR₂)₂] structure regardless of whether aliphatic or aromatic ligands are employed. The real-time (RT) TDDFT method is rapidly gaining prominence as an alternative approach to capture optical properties of molecular systems. A systematic benchmark study is performed to demonstrate the consistency of linear-response (LR) and RT-TDDFT methods for calculating the optical absorption spectra of a variety of bare gold and silver nanoparticles with different sizes and shapes.
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Mancini, Lorenzo. "Adiabatic and local approximations for the kohn-sham potential in the hubbard model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amslaurea.unibo.it/5935/.
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We obtain the exact time-dependent Kohn-Sham potentials Vks for 1D Hubbard chains, driven by a d.c. external field, using the time-dependent electron density and current density obtained from exact many-body time-evolution. The exact Vxc is compared to the adiabatically-exact Vad-xc and the “instantaneous ground state” Vigs-xc. The effectiveness of these two approximations is analyzed. Approximations for the exchange-correlation potential Vxc and its gradient, based on the local density and on the local current density, are also considered and both physical quantities are observed to be far outside the reach of any possible local approximation. Insight into the respective roles of ground-state and excited-state correlation in the time-dependent system, as reflected in the potentials, is provided by the pair correlation function.
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Caramella, Lucia. "Theoretical spectroscopy of realistic condensed matter systems." Paris 6, 2009. http://www.theses.fr/2009PA066019.
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Le sujet de cette these porte sur des calculs ab initio de proprietes d'etat fondamental et excite de systemes differents, dans le cadre de la dft et de la tddft. Du cote numerique, nous avons mis en oeuvre une methode originale pour l'evaluation de la polarisabilite dynamique a particules independantes, et generalise un code au spin dans le but d'etudier les proprietes magnetiques de systemes reels. Nous avons etudie des spectres de reflectivite anisotrope et de perte d'energie pour la surface (100) du silicium, propre ou oxydee. La comparaison entre les spectres mesures et simules, nous ont permis d'exclure la reconstruction p(2x1). En suite, nous avons mis en evidence le probleme de la description des excitations des systemes a couche ouverte presente un etude des proprietes optiques d'alliage magnetique interessants pour des applications en spintronique. Nous avons evalue les proprietes d'etat fondamental de ces alliages et la conductivite du fer ccc.
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Karimova, Natalia Vladimirovna. "Theoretical study of the optical properties of the noble metal nanoparticles: CD and MCD spectroscopy." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38177.
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Doctor of PhilosophyDepartment of Chemistry
Christine M. Aikens
Gold and silver particles with dimensions less than a nanometer possess unique characteristics and properties that are different from the properties of the bulk. They demonstrate a non–zero HOMO–LUMO gap that can reach up to 3.0 eV. These differences arise from size quantization effects in the metal core due to the small number of atoms. These nanoparticles have attracted great interest for decades both in fundamental and applied research. Small gold clusters protected by various types of ligands are of interest because ligands allow obtaining gold nanoclusters with given sizes, shapes and properties. Three main families of organic ligands are usually used for stabilization of gold nanoclusters: phosphine ligands, thiolate ligands and DNA. Usually, optical properties of these NPs are studied using optical absorption spectroscopy. Unfortunately, sometimes this type of spectrum is poorly resolved and tends to appear very similar for different complexes. In these cases, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopy can be applied. However, the interpretation of experimental CD and MCD spectra is a complicated process. In this thesis, theoretically simulated CD and MCD spectra were combined with optical absorption spectra to study optical activity for octa– and nona– and undecanuclear gold clusters protected by mono– and bidentate phosphine ligands. Additionally, optical properties of bare and DNA protected silver NPs were studied. Theoretical CD spectra were examined to learn more about the origin of chirality in chiral organometallic complexes, and to contribute to the understanding of the difference in chiroptical activity of gold clusters stabilized by different phosphine ligands and DNA–stabilized silver clusters. Furthermore, optical properties of the small centered gold clusters Au₈(PPh₃)₈²⁺ and Au₉(PPh₃)₈³⁺ were examined by optical absorption and MCD spectra using TDDFT. Theoretical MCD spectra were also used to identify the plasmonic behavior of silver nanoparticles. These results showed that CD and MCD spectroscopy yield more detailed information about optical properties and electronic structure of the different chemical systems than optical absorption spectroscopy alone. Theoretical simulation of the CD and MCD spectra together with optical absorption spectra can be used to assist in the understanding of empirically measured CD and MCD and provide useful information about optical properties and electronic structure.
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Bergstedt, Mikael. "Theoretical investigation of the first-order hyperpolarizability in the two-photon resonant region." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-10290.
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Time-dependent density functional theory calculations have been carried out to determine the complex first-order hyperpolarizability in the two-photon resonance region of the molecule IDS-Cab. Calculations show that three strongly absorbing states, in the ultraviolet region, are separated to the extent that no significant interference of the imaginary parts of the tensor elements of the first-order hyper-polarizability occurs. Consequently, and in contrast to experimental findings [27], no reduced imaginary parts of the first-order hyperpolarizability in the two-photon resonant region can be seen.
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Natarajan, Bhaarathi. "Implémentation et applications d'algorithmes fondés sur la théorie de la fonctionnelle de la densité dépendante du temps dans les logiciels à la base des fonctions gaussiennes et ondelettes." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00682011.
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L'interaction entre la matière et le rayonnement est un domaine bien établi de la physique. Pour un physico-chimiste, cette interaction peut être utilisée comme une sonde (spectroscopie) ou pour provoquer des réactions chimiques (photo-chimie). Les mécanismes des réactions photochimiques sont difficiles à étudier expérimentalement et même les études les plus sophistiquées de spectroscopies femtosecondes peuvent bénéficier énormément des simulations théoriques.Les résultats spectroscopiques d'ailleurs ont souvent besoin des calculs théoriques pour l'analyse de leurs spectres. Les méthodes théoriques pour décrire les processus photochimiques ont été principalement développées en utilisant le concept de la fonction d'onde à N corps et ont eu des succès remarquables. Cependant de telles approches sont généralement limitées à des petites ou moyennes molécules. Heureusement la théorie de la fonctionnelle de la densité dépendant du temps (TD-DFT) a émergé comme une méthode simple de calcul pouvant être appliquée à des molécules plus grandes, avec une précision qui est souvent, mais pas toujours, semblable à la précision provenant des méthodes basés sur la fonction d'onde à N électrons. Une partie de cette thèse consiste à surmonter les difficultés des approximations utilisées de nos jours en TD-DFT. En particulier, nous avons examiné la qualité des intersections coniques quand l'approche du retournement de spin non collinéaire de Ziegler-Wang est utilisée et nous avons montré que l'approche du retournement de spin, parfois ,améliore dans des cas particuliers, mais que c'est n'est pas une solution générale pour mieux décrire les intersections coniques dans les simulations photochimiques basées sur la TD-DFT. La plupart des parties de cette thèse traite d'améliorations algorithmiques, soit pour améliorer l'analyse des résultats de la TD-DFT, soit pour étendre les calculs de TD-DFT à de grandes molécules. L'implémentation de l'analyse automatique des symétries des orbitales moléculaires dans deMon2k est une contribution pour améliorer l'analyse des résultats de la TD-DFT. Cela a aussi servi comme une introduction au projet de programmation majeur. La contribution méthodologique principale dans cette thèse est l'implémentation des équations de Casida dans le code BigDFT fondé sur le formalisme des ondelettes. Cette implémentation a aussi permis une analyse détaillée des arguments positifs et négatifs de l'utilisation de la TD-DFT fondée sur les ondelettes. On montre qu'il est plus facile d'obtenir des orbitales moléculaires précises qu'avec deMon2k. Par contre, la contribution des orbitales inoccupées est plus problématiques qu'avec un code de gaussienne comme deMon2k. Finalement, les équations de base des gradients analytiques des états excités sont dérivées pour la TD-DFT. La thèse se termine avec quelques perspectives de travaux futurs.
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Guidez, Emilie Brigitte. "Quantum mechanical origin of the plasmonic properties of noble metal nanoparticles." Diss., Kansas State University, 2014. http://hdl.handle.net/2097/17314.
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Doctor of PhilosophyDepartment of Chemistry
Christine M. Aikens
Small silver and gold clusters (less than 2 nm) display a discrete absorption spectrum characteristic of molecular systems whereas larger particles display a strong, broad absorption band in the visible. The latter feature is due to the surface plasmon resonance, which is commonly explained by the collective dipolar motion of free electrons across the particle, creating charged surface states. The evolution between molecular properties and plasmon is investigated. Time-dependent density functional theory (TDDFT) calculations are performed to study the absorption spectrum of cluster-size silver and gold nanorods. The absorption spectrum of these silver nanorods exhibits high-intensity longitudinal and transverse modes (along the long and short axis of the nanorod respectively), similar to the plasmons observed experimentally for larger nanoparticles. These plasmon modes result from a constructive addition of the dipole moments of nearly degenerate single-particle excitations. The number of single-particle transitions involved increases with increasing system size, due to the growing density of states available. Gold nanorods exhibit a broader absorption spectrum than their silver counterpart due to enhanced relativistic effects, affecting the onset of the longitudinal plasmon mode. The high-energy, high-intensity beta-peak of acenes also results from a constructive addition of single-particle transitions and I show that it can be assigned to a plasmon. I also show that the plasmon modes of both acenes and metallic nanoparticles can be described with a simple configuration interaction (CI) interpretation. The evolution between molecular absorption spectrum and plasmon is also investigated by computing the density of states of spherical thiolate-protected gold clusters using a charge-perturbed particle-in-a-sphere model. The electronic structure obtained with this model gives good qualitative agreement with DFT calculations at a fraction of the cost. The progressive increase of the density of states with particle size observed is in accordance with the appearance of a plasmon peak. The optical properties of nanoparticles can be tuned by varying their composition. Therefore, the optical behavior of the bimetallic Au[subscript](25-n)Ag[subscript]n(SH)[subscript]18[superscript]- cluster for different values of n using TDDFT is analyzed. A large blue shift of the HOMO-LUMO absorption peak is observed with increasing silver content, in accordance with experimental results.
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Caserta, Mario. "Dinamica degli stati eccitati della formaldeide tramite teoria del funzionale-densità dipendente dal tempo in tempo reale." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19529/.
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In questo lavoro abbiamo studiato lo stato fondamentale e gli stati eccitati della molecola di formaldeide, che rappresenta il più semplice fra tutti i composti organici contenenti il gruppo carbonile. In particolare abbiamo analizzato l'accoppiamento fra le eccitazioni vibrazionali e le eccitazioni elettroniche. Lo studio è stato realizzato tramite Teoria del Funzionale-Densità (DFT) e Teoria del Funzionale-Densità Dipendente dal Tempo (TDDFT) nei regimi di Risposta Lineare (LR-TDDFT) e di propagazione in Tempo Reale (RT-TDDFT), nell'ambito dell'approssimazione di densità locale (LDA) per il funzionale di scambio e correlazione e dell'approssimazione di campo medio di Ehrenfest per la dinamica semiclassica in tempo reale del sistema accoppiato elettroni-nuclei.
Nella prima parte sono state caratterizzate le superfici potenziali dello stato fondamentale e degli stati elettronici eccitati determinate da moti nucleari relativi all'attivazione di un singolo modo normale, nel contesto della dinamica dei nuclei quasi-statica di Born-Oppenheimer. Le superfici potenziali sono state ottenute per lo stato fondamentale tramite DFT e per gli stati eccitati tramite LR-TDDFT.
Nella seconda parte del lavoro, tramite un'opportuna scelta di configurazioni iniziali distorte, sono state eseguite delle simulazioni di dinamica molecolare delle eccitazioni elettroniche-nucleari accoppiate. Queste simulazioni sono state svolte nell'ambito della RT-TDDFT/Ehrenfest. Per queste eccitazioni accoppiate sono state analizzate e caratterizzate le oscillazioni nucleari attivate e le configurazioni geometriche molecolari.
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Oksuz, Nevin. "Quantum-chemical Study Of Geometrical And Electronic Structures Of Aromatic Five-membered Heterocyclic Oligomers In The Ground And Lowest Singlet Excited States." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605397/index.pdf.
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The nature of the ground state and the first (lowest) singlet excited state geometrical conformations and electronic transitions in the aromatic five-membered heterocyclic oligomers &ndasholigothiophenes (nT), oligofurans (nF), and oligopyrroles (nP)- containing up to six monomer units (total of 18 molecules) were explored using several computational methodologies. Geometry optimizations were carried out at Austin Model 1 (AM1), Restricted Hartree-Fock (RHF/6-31G*), and Density Functional Theory (DFT, B3LYP/6-31G*) levels for the ground-state conformations of these structurally well-defined heterocyclic oligomers. The Configuration Interaction Singles (CIS) method with the 6-31G* basis set was chosen in computation of the optimal geometry of the lowest singlet excited state. Lowest singlet excitation S1ß
S0 energies were calculated using the Zerner&rsquo
s Intermediate Neglect of Differential Overlap for Spectroscopy (ZINDO/S), CIS (CIS/6-31G*), and Time-Dependent DFT (TDDFT/6-31G* and TDDFT/6-31+G*) methods. In computation of the emission S1à
S0 energies, we have employed all methods above except ZINDO/S. In investigation of geometries of the ground and lowest singlet excited state, we compared the bond length alternation (BLA) parameters, Dri in the conjugated backbone of the oligomers. Saturation of the geometrical parameters at the center of oligomers was observed after a certain chain length. Among all methodologies used in computation of excitation (S1ß
S0) and emission (S1à
S0) energies, TDDFT results showed the best agreement with experimental data. Fits of computed and experimental excitation energies to an exponential function using the least squares method enabled us to predict Effective Conjugation Length (ECL) values. We obtained the ECLs of 17 (17), 16 (15), and 14 (13) monomer units for polythiophene (PTh), polyfuran (PFu), and polypyrrole (PPr), which have very good agreement with the results obtained from the fits of experimental data (the values in parentheses).
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Yuen-Zhou, Joel. "A Quantum Information Approach to Ultrafast Spectroscopy." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10317.
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In the first part of the dissertation, we develop a theoretical approach to analyze nonlinear spectroscopy experiments based on the formalism of quantum state (QST) and process tomography (QPT). In it, a quantum system is regarded as a black box which can be systematically tested in its performance, very much like an electric circuit is tested by sending a series of inputs and measuring the corresponding outputs, but in the quantum sense. We show how to collect a series of pump-probe or photon-echo experiments, and by varying polarizations and frequency components of the perturbations, reconstruct the quantum state (density matrix) of the probed system for a set of different initial conditions, hence simultaneously achieving QST and QPT. Furthermore, we establish the conditions under which a set of two-dimensional optical spectra also yield the desired results. Simulations of noisy experiments with inhomogeneous broadening show the feasibility of the protocol. A spin-off of this work is our suggestion of a witness that distinguishes between spectroscopic time-oscillations corresponding to vibronic only coherences against their electronic counterparts. We conclude by noting that the QST/QPT approach to nonlinear spectroscopy sheds light on the amount of quantum information contained in the output of an experiment, and hence, is a convenient theoretical and experimental paradigm even when the goal is not to perform a full QPT. In the second part of the thesis, we discuss a methodology to study the electronic dynamics of complex molecular systems, such as photosynthetic units, in the framework of time-dependent density functional theory (TD-DFT). By treating the electronic degrees of freedom as the system and the nuclear ones as the bath, we develop an open quantum systems (OQS) approach to TD-DFT. We formally extend the theoretical backbone of TD-DFT to OQS, and suggest a Markovian bath functional which can be readily included in electronic structure codes.
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Migliore, Mattia. "Recherche par modélisaion moléculaire de signatures RMN et DC caractéristiques pour les coudes β et y dans les peptides bioactifs. Characterization of β-turns by electronic circular dichroism spectroscopy : a coupled molecular dynamics and time-dependent density functional theory computational study." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR001.
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Ce travail de thèse a porté sur la recherche, par modélisation moléculaire, de signatures RMN et DC caractéristiques pour les coudes γ et β dans les peptides bioactifs. Les coudes γ et β, avec les hélices, constituent des motifs privilégiés de reconnaissance des peptides bioactifs par leurs cibles. Or, bien qu’il existe, au sein des structures de polypeptides, plusieurs catégories de coudes possédant des géométries différentes (2 types de coudes γ et 12 types de coudes β), peu d’outils expérimentaux sont disponibles pour aider à leur distinction. Ainsi, seuls 4 types de coudes β (I, I’, II et II’) ont, pour l’instant été caractérisés par RMN et il n’existe pas de spectre DC de référence fiable pour aucun motif de type coude. Dans un premier temps, afin d’élargir la base de données de RMN pour tous les types de coudes β (I, I’, II, II’, IV₁, IV₂, IV₃, IV₄, Via1, Via2, VIb et VIII) et γ (classique et inverse), nous avons analysé les paramètres structuraux caractéristiques de RMN (distances inter-hydrogènes et constantes de couplages ᶾJʜɴ-ʜꭤ) sur un ensemble de peptides modèles, extraits de la banque de protéines PDB et représentatifs de ces coudes. Les analyses des distances inter-hydrogènes ont permis d’identifier des signatures RMN caractéristiques pour différencier les deux types de coudes γ et certains types de coudes β (IV₁, IV₂,, VIb et VIII). La constante de couplage ᶾJʜɴ-ʜꭤ pourra servir à confirmer l’identification et à lever des ambiguïtés. Dans un second temps, en couplant dynamique moléculaire et TDDFT, nous avons simulé les spectres de DC de référence de peptides modèles adoptant des conformations de coudes β de type I, I’, II et II’. Les simulations ont permis de discerner deux familles de spectres DC caractéristiques : les types I/II’ d’un côté et les types I’/II de l’autre. L’ensemble de ces résultats indique que les coudes ne présentent pas nécessairement les mêmes signatures pour les deux techniques. La combinaison des signatures discriminantes de RMN et de DC pourrait donc permettre une meilleure identification des natures et des différents types de coudesThe aim of this work is to identify NMR and CD characteristic patterns for β- and γ-turns in bioactive peptides by molecular modelling. With helices, β- and γ-turns constitute favoured recognition motifs in bioactive peptides by their targets. Even though several classes of turns with different geometries exist in polypeptide structures (2 γ-turn types and 12 β-turn types), few experimental tools are available for their characterization. Thus, only 4 types of β-turns (I, I’, II et II’) have been, at present, described by NMR and there are no reliable reference CD spectra for turns. In order to extend the NMR data for all β- and γ-turn types, we analyzed NMR structural parameters (inter-hydrogen distances and ᶾJʜɴ-ʜꭤ coupling constants) in a representative peptide model dataset extracted from the PDB. The inter-hydrogen distance analysis allowed to identify specific NMR patterns for the two γ-turn types and for four β-turn types (IV₁, IV₂,, VIb and VIII). ᶾJʜɴ-ʜꭤ coupling constant may be used to confirm the identification and to remove ambiguities. Then, we simulated the reference CD spectra of model peptides adopting type I, I’, II and II’ β-turn conformations by combining molecular dynamic simulations and TDDFT computations. These computations allowed to determine two families of specific CD spectra : types I/II’, on one side and types I’/II, on the other. All these results indicate that the turns do not present the same patterns in both techniques. The combination of NMR and CD could therefore allow a better identification of the nature and the different types of turns
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Sinha, Roy Rajarshi. "Ab initio simulation of optical properties of noble-metal clusters." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0017/document.
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L'intérêt de la recherche fondamentale pour les morceaux nanométriques de métaux nobles est principalement dû à la résonance localisée des plasmons de surface (LSPR) dans l'absorption optique. Différents aspects, liés à la compréhension théorique de la LSPR dans le cas de clusters de métaux nobles de taille dite intermédiaire, sont étudiés dans ce manuscrit. Afin d'avoir une vision plus large nous utilisons deux approches : l'approche électromagnétique classique et le formalisme ab initio en temps réel de la théorie de la fonctionnelle de la densité dépendant du temps (RT-TDDFT). Une comparaison systématique et détaillée de ces deux approches souligne et quantifie les limitations de l'approche électromagnétique lorsqu'elle est appliquée à des systèmes de taille quantique. Les différences entre les excitations plasmoniques collectives et celles impliquant les électrons d, ainsi que leurs interactions, sont étudiées grâce au comportement spatial des densités correspondantes. Ces densités sont obtenues en appliquant une transformée de Fourier dans l'espace à la densité obtenue par les simulations DFT utilisant une perturbation delta-kick. Dans ce manuscrit, des clusters de métaux nobles nus et protégés par des ligands sont étudiés. En particulier, motivé par de récents travaux sur les phénomènes d'émergence de plasmon, l'étude par TD-DFT de nano-alliages Au-Cu de taille tout juste inférieure à 2nm à fourni de subtiles connaissances sur les effets d'alliages sur la réponse optique de tels systèmesThe fundamental research interest in nanometric pieces of noble metals is mainly due to the localized surface-plasmon resonance (LSPR) in the optical absorption. Different aspects related to the theoretical understanding of LSPRs in `intermediate-size' noble-metal clusters are studied in this thesis. To gain a broader perspective both the real-time \ai formalism of \td density-functional theory (RT-TDDFT) and the classical electromagnetics approach are employed. A systematic and detailed comparison of these two approaches highlights and quantifies the limitations of the electromagnetics approach when applied to quantum-sized systems. The differences between collective plasmonic excitations and the excitations involving $d$-electrons, as well as the interplay between them are explored in the spatial behaviour of the corresponding induced densities by performing the spatially resolved Fourier transform of the time-dependent induced density obtained from a RT-TDDFT simulation using a $\delta$-kick perturbation. In this thesis, both bare and ligand-protected noble-metal clusters were studied. In particular, motivated by recent experiments on plasmon emergence phenomena, the TDDFT study of Au-Cu nanoalloys in the size range just below 2~nm produced subtle insights into the general effects of alloying on the optical response of these systems
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Vieira, Daniel. "Correções de auto-interação na teoria do funcional da densidade: investigação em modelos de sistemas de muitos corpos." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-23042010-101040/.
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Neste trabalho utilizamos sistemas modelos no desenvolvimento, implementação e análise de funcionais orbitais da densidade, focando, em particular, nas correções de autointeração de Perdew-Zunger (PZSIC) e Lundin-Eriksson (LESIC). Aplicamos as correções de auto-interação ao funcional local (LDA) do modelo de Hubbard e de poços quânticos semicondutores, ambos unidimensionais, no caso estático e dependente do tempo, respectivamente. Para o modelo de Hubbard unidimensional, comparamos a LDA, LDA+PZSIC e LDA+LESIC, identificando o desempenho para energias e densidades do estado fundamental, com e sem impurezas locais, além do gap fundamental de energia. Em adição, averiguamos o desempenho diante de cargas fracionárias, estabelecendo conexões com o erro de delocalização da LDA. Mostramos a possibilidade da correta descrição das freqüências das oscilações de Friedel no modelo de Hubbard, além de investigar como a falha da LDA em reproduzir esse aspecto pode estar relacionada com os erros de auto-interação e delocalização. Investigamos ainda as diferentes possibilidades de implementação autoconsistente de qualquer funcional orbital da densidade, analisando a relação entre funcionais aproximados e suas implementações aproximadas. Nos poços quânticos, sob o enfoque dependente do tempo, analisamos a descontinuidade do potencial de troca e correlação ao variarmos o número de partículas, em dois processos distintos: a ionização eletrônica em um poço simples e dissociação de um poço duplo assimétrico. No último caso, avaliamos os efeitos da descontinuidade no número total de partículas em cada poço, revelando os mecanismos que resgatam a neutralidade elétrica durante processos de dissociação, com a correta carga final inteira.In this work we use model systems to develop, implement and analyse orbital-dependent density functionals, focusing, specifically, on the self-interaction corrections (SICs) of Perdew and Zunger (PZSIC) and of Lundin and Eriksson (LESIC). These self-interaction corrections are applied to the local-density approximation (LDA) for the one-dimensional Hubbard model and for semiconductor quantum wells, in one-dimensional static and time-dependent situations. For the one-dimensional Hubbard model we compare LDA, LDA+PZSIC and LDA+LESIC, and investigate the performance of these approaches for ground-state energies, densities and energy gaps, with and without impurities in the system. We also consider the case of fractional charges, where a connection to the delocalization error of the LDA can be made. We show that in principle a correct description of the frequences of Friedel oscillations in the Hubbard model can be obtained from DFT, and investigate how the failure of the LDA in reproducing this is related to the selfinteraction and delocalization errors. Moreover, we investigate different procedures for the selfconsistent implementation of any orbital-dependent functional, and analyse the question of the interplay between an approximate functional and its approximate implementation. For quantum wells sytems we analyse, in a time-dependent framework, the discontinuity of the exchange-correlation potential under variation of the particle number in two different processes: the ionization of a simple quantum well and the dissociation of an asymmetric double well. In the latter case, we also consider the effect of changes in the particle number in each subwell, thus revealing the mechanism that restores electric neutrality during dissociation, with correct final charge.
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Fradon, Alexis. "Design de polymères conjugués pour des applications dans le photovoltaïque assisté par modélisation moléculaire." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0310/document.
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Ces dernières années, un nouveau type de polymère donneur d’électron pour des applications photovoltaïques a été étudié de manière intensive, les copolymères à faible bande interdite. Ils sont constitués d’un groupement riche en électron (ER) et d’un groupement pauvre (EP) permettant de contrôler les orbitales frontières et d’induire une délocalisation de l’exciton généré lors du processus de photo-excitation. Une large variété de dispositifs est basée sur ces copolymères avec des rendements d’environ 10% et, pour accroitre leur efficacité, il est nécessaire d’avoir une meilleure compréhension de ces polymères pendant le phénomène de photo-absorption. La chimie théorique apparait comme un outil permettant de prédire différentes propriétés optoélectroniques. Au cours de ce travail, nous avons utilisé la théorie de la fonctionnelle de la densité indépendante (DFT) et dépendante du temps (TD DFT) pour simuler les propriétés optiques d’oligomères de taille croissante avec différents groupements ER et EP. Les propriétés optiques des polymères correspondant ont été extrapolées à l’aide du modèle de Kuhn. Ce criblage théorique nous a permis de sélectionner des systèmes prometteurs à base de benzodithiophène, de benzothiadiazole et de benzofurazane qui ont ensuite été synthétisés par couplage de Stille. Les polymères et oligomères obtenus ont été caractérisés par spectroscopie UV-visible et de fluorescence, chromatographie d’exclusion stérique et par RMN dans le but d’observer des relations structure-propriétés et de faire des corrélations entre résultats expérimentaux et théoriquesDuring the last decade, a new kind of donor polymers for photovoltaic application have been intensively studied, the low band-gap polymers. They are based on repeating units associating two different moieties, one electron-rich (ER) and one electron-poor (EP), which allow to finely tune the molecular orbitals and to induce a delocalization of the exciton generated upon the photo-excitation process. A large variety of devices are based on such low band-gap polymers, with a power conversion efficiency record around 10%, and, to increase the efficiency, it is necessary to have a better understanding of these polymers during the photo-absorption phenomenon. Computational chemistry isa powerful tool that permits to predict different opto-electronic properties. For this work, we used Density Functional Theory and Time-Dependent Density Functional Theory to compute the optical properties of increasingly large oligomers involving various ER and EP subunits. The optical properties in the polymer limit were then estimated for the different systems by using an extrapolation scheme based on the Kuhn equation. This theoretical screening allowed us to select promising candidates based on benzodithiophene, benzothiadiazole and benzofurazan for syntheses, which were performed by a Stille coupling. The obtained polymers and size-controlled oligomers were further characterized by UV visible spectroscopy, fluorescence, size exclusion chromatography and NMR, in order to extractstructure-properties relationships and correlate experimental results to theoretical data
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Carter-Fenk, Kevin D. "Design and Implementation of Quantum Chemistry Methods for the Condensed Phase: Noncovalent Interactions at the Nanoscale and Excited States in Bulk Solution." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu161617640330551.
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Messud, Jérémie. "Théorie de la fonctionnelle de la densité dépendant du temps avec correction d'auto-intéraction." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/626/.
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La Théorie de la Fonctionnelle de la Densité dépendant du temps constitue un outil de choix pour l'étude des mécanismes élémentaires d'irradiation moléculaire. Mais les approximations qui lui sont inhérentes n'éliminent pas un effet non physique appelé auto-intéraction, ce qui fausse complètement les propriétés d'irradiation. La voie la plus prometteuse permettant de supprimer l'auto-intéraction sans introduire aucun paramètre libre supplémentaire est d'utiliser des fonctionnelles "orbitales dépendantes" (méthodes SIC). Seulement, le formalisme usuel qui en découle n'est pas hermitique, faussant dramatiquement les prédictions physiques dans le cas dynamique, et les tentatives visant à rétablir l'hermiticité connaissent toutes des pathologies indésirables. Ainsi, la question, dans le cas dépendent du temps, d'un formalisme SIC exact (TDSIC), satisfaisant les lois de conservation et numériquement manipulable reste une question ouverte. Nous proposons une nouvelle formulation purement variationnelle, contraignant l'orthonormalité et utilisant le degré de liberté de transformation unitaire. Cela permet d'écrire les équations TDSIC exactes sous une forme hermitique (dans le sous espace occupé), satisfaisant toutes les lois de conservation et menant à un schéma numérique de propagation clair. Le prix à payer est que le hamiltonien résultant est explicitement non local, ce qui est plus gourmand numériquement parlant. Cela nous a conduit à proposer, dans un deuxième temps, une approximation locale particulièrement intéressante, que nous avons baptisée "Generalized SIC-Slater". Enfin, nous proposons un ensemble de résultats numériques sur des systèmes moléculaires variés afin de soumettre les formalismes développés au verdict de la nature et les comparer aux formalismes SIC usuelsTime dependent Density Functional Theory is a tool of choice to study elementary molecular irradiation processes. But the approximations that are inherent do not eliminate an unphysical effect called self-interaction, which completely distorts the irradiation properties. The most promising way to remove the self-interaction without introducing any additional free parameter is to use orbital dependent functionals (SIC methods). But the usual formalism that follows is not hermitian, which dramatically distorts the physical predictions in the dynamical case, and attempts to restore hermiticity know all undesirable pathologies. So the question, in the time dependent case, of an exact SIC formalism (TDSIC) which would satisfy all the conservation laws and would be numerically manageable remains an open question. We propose a new purely variational formulation, enforcing the orthonormality and using the unitary transformation degree of freedom. This allows to write the exact TDSIC equations in an hermitian form (in the occupied subspace), which satisfies all the conservation laws and leads to a clear numerical scheme for propagation. The price to pay is that the resulting hamiltonian is explicitly non-local, which is more costly numerically speaking. This led us to propose, in a second step, a particularly interesting local approximation, which we called "Generalized SIC-Slater". Finally, we propose a set of numerical results on various molecular systems in order to submit the developed formalisms to the verdict of nature and to compare them with the usual SIC formalism
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Magero, Denis. "Electrochemical and photochemical studies of some remarkable ruthenium complexes." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV071/document.
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Cette thèse fait partie d’un projet franco-keyan dénommé ELEPHOX (ELEctrochemical and PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes). En particulier, notre focus est la continuation du travail de C. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin, Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, et Mark E. Casida, “Density-Functional Study of Lumininescence in Polypyridine Ruthenium Complexes,” J. Photochem. and Photobiol. A 276, 8 (2014). Cet article a proposé une indice orbitalaire de temps de luminescence pour les complexesde ruthénium. Cependant cet article n’était limité qu’à quelques mnolecules. Afin d’avoir une théorie plus fiable et donc potentiellement plus utile, il faudra tester l’indice de luminescence sur beaucoup plus de molécules. Ayant établi le protocol, il était “évident” mais toujours un défi de le tester sur encore une centaine de molécules pour démonter ou infirmer l’indice proposée. Pour ce faire, j’ai examainé les 98 pages de la Table I de A. Juris, V. Balzani, F. Bargelleti, S. Campagna, P. Belser, et A.V. Zelewsky, “Ru(II) polypyridine complexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,” Chem. Rev. 84, 85 (1988) et j’ai extrait un nombre important de données susceptibles à comparaison avec les résultats des calculs de la théorie de la fonctionelle de la densité (DFT) et la DFT dépendante du temps (TD-DFT). Comme les résultats étaient suffisament encourageant, le modèle DFT était examiné de plus près avec la méthode d’une théorie de champs de ligands (LFT) à la base de la densité des états partielle (PDOS). Ainsi j’ai pu tester l’indice de luminescence proposée précédement par laméthode PDOS-LFT et j’ai trouvé des difficultés avec l’indice initialement proposée. Par contre, nous avons pu proposer une nouvelle indice de luminescence qui, à quelques exceptions près, a une corrélation linéaire avec une barrière énergétique moyenne pour l’état triplet excité dérivée à partir des données experimentales. À l’avenir nous pouvons proposer une investigation plus directe de la barrière sur la surface triplet excité pour remplacer la valeur approximative déduite de l’expérience. Puis nous voulons voir sinotre indice de luminescence s’appliquent aux cas des complexes d’iridiumThis thesis is part of the Franco-Kenyan project ELEPHOX (ELEctrochemicaland PHOto Properties of Some Remarkable Ruthenium and Iron CompleXes)project. In particular, it focused on the continuation of the work ofC. Muhavini Wawire, Damien Jouvenot, Fréd erique Loiseau, Pablo Baudin,Sébastien Liatard, Lydia Njenga, Geoffrey Kamau, and Mark E. Casida,“Density-Functional Study of Lumininescence in Polypyridine RutheniumComplexes,” J. Photochem. and Photobiol. A 276, 8 (2014). That paperproposed a luminescence index for estimating whether a ruthenium complexwill luminesce or not. However that paper only tested the theory ona few molecules. In order for the theory to have a significant impact, itmust be tested on many more molecules. Now that the protocol has beenworked out, it was a straightforward but still quite challenging matter todo another 100 or so molecules to prove or disprove the theory. In order todo so, I went through the 98 pages of Table I of A. Juris, V. Balzani, F.Bargelleti, S. Campagna, P. Belser, and A.V. Zelewsky, “Ru(II) polypyridinecomplexes: Photophysics, photochemistry, electrochemistry, and chemiluminescence,”Chem. Rev. 84, 85 (1988) and extracted data suitable for comparingagainst density-functional theory (DFT) and time-dependent (TD-)DFT.Since the results were sufficiently encouraging, the DFT model was examinedin the light of partial density of states ligand field theory (PDOS-LFT) andthe previously proposed luminescence indices were tested. In fact, the originallyproposed indices were not found to be very reliable but we were able topropose a new luminescence index based upon much more data and in analogywith frontier-molecular orbital ideas. Except for a few compounds, this index provides a luminescence index with a good linear correlation with anexperimentally-derived average excited-state activation energy barrier. Futurework should be aimed at both explicit theoretical calculations of thisbarrier for ruthenium complexes and extension of the luminescence indexidea to iridium complexes
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Fischer, Michael. "Non-adiabatic quantum molecular dynamics: - Benchmark systems in strong laser fields - Approximate electron-nuclear correlations." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-148848.
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The non-adiabatic quantum molecular dynamics (NA-QMD) method couples self-consistently classical nuclear motion with time-dependent density functional theory (TDDFT) in basis expansion for the electron dynamics. It has become a versatile approach to study the dynamics of atoms, molecules and clusters in a wide range of scenarios. This work presents applications of the NA-QMD method to important benchmark systems and its systematic extension to include quantum effects in the nuclear motion.
Regarding the first objective, a complete study of the strong-field ionization and dissociation dynamics of nature’s simplest molecule H2+ is performed. By including all electronic and nuclear degrees of freedom and all reaction channels, molecular rotation is shown to play an important role in the ionization process. In addition, strong orientation effects in the energy deposition process of the Buckminster fullerene C60 in short intense laser pulses are surprisingly found in full dimensional calculations. Their consequences on the subsequent nuclear relaxation dynamics shed new light on available experimental data and future experiments are proposed to confirm the detailed predictions.
Regarding the second objective, the NA-QMD formalism is basically extended to take electron-nuclear correlations into account. This extension is achieved by means of a trajectory surface hopping scheme in the adiabatic Kohn-Sham framework. First studied examples from collision physics and photochemistry illustrate the relevance and importance of quantum effects in the nuclear dynamics.
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Garcia, Ricardo D\'Agostino. "Modelagem molecular (TD-DFT) aplicada à simulação de espectros UV para cinamatos com perfil de filtros solares." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/9/9138/tde-11082014-162702/.
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O câncer de pele se apresenta como um sério problema de saúde pública mundial, sendo incidente nos cinco continentes. As ações relacionadas à prevenção dessa doença envolvem, entre outras coisas, a utilização de protetores solares e a educação em saúde. Em virtude do aumento do número de indivíduos com câncer de pele a cada ano, é de grande valor estudos de entendimento e desenvolvimento de filtros solares melhores e mais seguros. Os produtos utilizados com a finalidade de proteger a pele dos raios solares ultravioletas (UV) possuem em sua composição filtros solares, que podem ter ação física, refletindo e dissipando a radiação UV; ou ação química, absorvendo a radiação UV. Os filtros químicos podem apresentar absorção em UVB (290-320 nm), UVA (320-400 nm) ou em ambas as faixas, sendo considerados de amplo espectro. . Dentre as várias classes de compostos com perfil de filtro solar UVB, os cinamatos destacam-se por apresentarem boa eficácia e excelente custo-benefício. A aplicação de cálculos teóricos tornou-se indispensável no planejamento de fármacos e nos estudos de mecanismo de ação de moléculas bioativas, visto a diminuição de tempo e custos em pesquisa e desenvolvimento. O desenvolvimento de métodos quânticos robustos, como o TD-DFT, permitiu a simulação de propriedades experimentais in silico, tais como espectros de RMN e UV. Diante deste panorama, aplicamos tal método na simulação de espectros UV para os cinamatos com perfil de filtros solares. Realizou-se uma busca do melhor funcional para simulação dos espectros, na qual se determinou que os funcionais B3LYP e B3P86 apresentaram melhores resultados quando comparados ao espectro experimental do composto p-metoxicinamato de etilexila determinado em metanol. Foram simulados os espectros de UV para sete compostos derivados do ácido cinâmico, os quais apresentaram λ máximo próximo a 310 nm, como descrito na literatura. Observou-se que a energia média para que ocorra a principal transição eletrônica, de HOMO para LUMO, é de 3,95 eV. O método mostrou-se adequado para a determinação de espectros UV para a classe dos cinamatos e pode ser utilizado na busca de novos compostos dessa classe a serem empregados como filtros solares.Skin cancer presents itself as a very serious world public health problem, being incident all over the five continents. Using sunscreen and receiving health education, among other factors, are related to prevent the disease. The number of people with skin cancer increases every year, therefore, studies for better knowledge and development for better and safer sunscreens are crucial. Products used with the intention to protect the skin from ultraviolet sunrays (UV) are partially composed by sunscreen, which may lead to two different reactions, a physical reaction, that reflects and ceases the UV radiation; or a chemical reaction, that absorbs the UV radiation. Chemical filters may present absorption in UVB (290-320 nm), UVA (320 400 nm) or in both, which is considered as broad spectrum. Among the various types of compound forms with sunscreen UVB profile, cinnamates stand out for presenting good efficiency and excellent cost-benefit. The application of theoretical calculations became essential for drug design and bioactive molecules action mechanism studies, considering time saving and costs in research and development. The development of robust quantum method, such as TD-DFT allowed the simulation of experimental properties in silico, like RMN and UV spectra. Given this overview, this method was applied to simulate UV spectra of cinnamates with sunscreen profile. A search was done to define the best functional to simulate all spectrum, where the functionals B3LYP and B3P86 showed the best results when compared to experimental spectra of the compound ethylhexyl methoxycinnamate determined in methanol. An UV spectrum simulation for seven compounds derived from cinnamic acid showed maximum wavelength around to 310 nm, as described in the literature. It was observed that the average energy for the main electronic transition, HOMO to LUMO, is 3,95 eV. The method proved to be adequate for the determination of UV spectra for cinnamate class and it can be used as a tool on the search for new compounds from this class to be used as sunscreen.
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Flick, Johannes. "Exact nonadiabatic many-body dynamics." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17581.
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Chemische Reaktionen in der Natur sowie Prozesse in synthetischen Materialien werden oft erst durch die Wechselwirkung von Licht mit Materie ausgelöst. Üblicherweise werden diese komplexen Prozesse mit Hilfe von Näherungen beschrieben. Im ersten Teil der Arbeit wird die Gültigkeit der Born-Oppenheimer Näherung in einem vibronischen Modellsystem (Trans-Polyacetylene) unter Photoelektronenspektroskopie im Gleichgewicht sowie zeitaufgelöster Photoelektronenspektroskopie im Nichtgleichgewicht überprüft. Die vibronische Spektralfunktion zeigt aufgrund des faktorisierten Anfangs- und Endzustandes in der Born-Oppenheimer Näherung zusätzliche Peaks, die in der exakten Spektralfunktion nicht auftreten. Im Nichtgleichgewicht zeigen wir für eine Franck-Condon Anregung und eine Anregung mit Pump-Probe Puls, wie die Bewegung des vibronischen Wellenpaktes im zeitabhängigen Photoelektronenspektrum verfolgt werden kann. Im zweiten Teil der Arbeit werden sowohl die Materie als auch das Licht quantisiert behandelt. Für eine volle quantenmechanische Beschreibung des Elektron-Licht Systems, verwenden wir die kürzlich entwickelte quantenelektrodynamische Dichtefunktionaltheorie (QEDFT) für gekoppelte Elektron-Photon Systeme. Wir zeigen erste numerische QEDFT-Berechnungen voll quantisierter Atome und Moleküle in optischen Kavitäten, die an das quantisierte elektromagnetische Feld gekoppelt sind. Mit Hilfe von Fixpunktiterationen berechnen wir das exakte Kohn-Sham Potential im diskreten Ortsraum, wobei unser Hauptaugenmerk auf dem Austausch-Korrelations-Potential liegt. Wir zeigen die erste Näherung des Austausch-Korrelations-Potentials mit Hilfe eines optimierten effektiven Potential Ansatzes angewandt auf einen Jaynes-Cummings-Dimer. Die dieser Arbeit zugrunde liegenden Erkenntnisse und Näherungen ermöglichen es neuartige Phänomene an der Schnittstelle zwischen den Materialwissenschaften und der Quantenoptik zu beschreiben.Many natural and synthetic processes are triggered by the interaction of light and matter. All these complex processes are routinely explained by employing various approximations. In the first part of this work, we assess the validity of the Born-Oppenheimer approximation in the case of equilibrium and time-resolved nonequilibrium photoelectron spectra for a vibronic model system of Trans-Polyacetylene. We show that spurious peaks appear for the vibronic spectral function in the Born-Oppenheimer approximation, which are not present in the exact spectral function of the system. This effect can be traced back to the factorized nature of the Born-Oppenheimer initial and final photoemission states. In the nonequilibrium case, we illustrate for an initial Franck-Condon excitation and an explicit pump-pulse excitation how the vibronic wave packet motion can be traced in the time-resolved photoelectron spectra as function of the pump-probe delay. In the second part of this work, we aim at treating both, matter and light, on an equal quantized footing. We apply the recently developed quantum electrodynamical density-functional theory, (QEDFT), which allows to describe electron-photon systems fully quantum mechanically. We present the first numerical calculations in the framework of QEDFT. We focus on the electron-photon exchange-correlation contribution by calculating exact Kohn-Sham potentials in real space using fixed-point inversions and present the performance of the first approximate exchange-correlation potential based on an optimized effective potential approach for a Jaynes-Cummings-Hubbard dimer. This work opens new research lines at the interface between materials science and quantum optics.
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Nayyar, Iffat. "Prediction of Optical Properties of Pi-Conjugated Organic Materials for Technological Innovations." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5993.
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Organic ?-conjugated solids are promising candidates for new optoelectronic materials. The large body of evidence points at their advantageous properties such as high charge-carrier mobility, large nonlinear polarizability, mechanical flexibility, simple and low cost fabrication and superior luminescence. They can be used as nonlinear optical (NLO) materials with large two-photon absorption (2PA) and as electronic components capable of generating nonlinear neutral (excitonic) and charged (polaronic) excitations. In this work, we investigate the appropriate theoretical methods used for the (a) prediction of 2PA properties for rational design of organic materials with improved NLO properties, and (b) understanding of the essential electronic excitations controlling the energy-transfer and charge-transport properties in organic optoelectronics. Accurate prediction of these electro-optical properties is helpful for structure-activity relationships useful for technological innovations.
In Chapter 1 we emphasize on the potential use of the organic materials for these two applications. The 2PA process is advantageous over one-photon absorption for deep-tissue fluorescence microscopy, photodynamic therapy, microfabrication and optical data storage owing to the three-dimensional spatial selectivity and improved penetration depth in the absorbing or scattering media. The design of the NLO materials with large 2PA cross-sections may reduce the optical damage due to the use of the high intensity laser beams for excitation. The organic molecules also possess self-localized excited states which can decay radiatively or nonradiatively to form excitonic states. This suggests the use of these materials in the electroluminescent devices such as light-emitting diodes and photovoltaic cells through the processes of exciton formation or dissociation, respectively. It is therefore necessary to understand ultrafast relaxation processes required in understanding the interplay between the efficient radiative transfer between the excited states and exciton dissociation into polarons for improving the efficiency of these devices. In Chapter 2, we provide the detailed description of the various theoretical methods applied for the prediction as well as the interpretation of the optical properties of a special class of substituted PPV [poly (p-phenylene vinylene)] oligomers.
In Chapter 3, we report the accuracy of different second and third order time dependent density functional theory (TD-DFT) formalisms in prediction of the 2PA spectra compared to the experimental measurements for donor-acceptor PPV derivatives. We recommend a posteriori Tamm-Dancoff approximation method for both qualitative and quantitative analysis of 2PA properties. Whereas, Agren's quadratic response methods lack the double excitations and are not suitable for the qualitative analysis of the state-specific contributions distorting the overall quality of the 2PA predictions. We trace the reasons to the artifactual excited states above the ionization threshold. We also study the effect of the basis set, geometrical constraints and the orbital exchange fraction on the 2PA excitation energies and cross-sections. Higher exchange (BMK and M05-2X) and range-separated (CAM-B3LYP) hybrid functionals are found to yield inaccurate predictions both quantitatively and qualitatively. The failure of the exchange-correlation (XC) functionals with correct asymptotic is traced to the inaccurate transition dipoles between the valence states, where functionals with low HF exchange succeed.
In Chapter 4, we test the performance of different semiempirical wavefunction theory methods for the prediction of 2PA properties compared to the DFT results for the same set of molecules. The spectroscopic parameterized (ZINDO/S) method is relatively better than the general purpose parameterized (PM6) method but the accuracy is trailing behind the DFT methods. The poor performances of PM6 and ZINDO/S methods are attributed to the incorrect description of excited-to-excited state transition and 2PA energies, respectively. The different semiempirical parameterizations can at best be used for quantitative analysis of the 2PA properties. The ZINDO/S method combined with different orders of multi-reference configuration interactions provide an improved description of 2PA properties. However, the results are observed to be highly dependent on the specific choice for the active space, order of excitation and reference configurations.
In Chapter 5, we present a linear response TD-DFT study to benchmark the ability of existing functional models to describe the extent of self-trapped neutral and charged excitations in PPV and its derivative MEH-PPV considered in their trans-isomeric forms. The electronic excitations in question include the lowest singlet (S1) and triplet (T1†) excitons, positive (P+) and negative (P-) polarons and the lowest triplet (T1) states. Use of the long-range-corrected DFT functional, such as LC-wPBE, is found to be crucial in order to predict the physically correct spatial localization of all the electronic excitations in agreement with experiment. The inclusion of polarizable dielectric environment play an important role for the charged states. The particle-hole symmetry is preserved for both the polymers in trans geometries. These studies indicate two distinct origins leading to self-localization of electronic excitations. Firstly, distortion of molecular geometry may create a spatially localized potential energy well where the state wavefunction self-traps. Secondly, even in the absence of geometric and vibrational dynamics, the excitation may become spatially confined due to energy stabilization caused by polarization effects from surrounding dielectric medium.
In Chapter 6, we aim to separate these two fundamental sources of spatial localization. We observe the electronic localization of P+ and P- is determined by the polarization effects of the surrounding media and the character of the DFT functional. In contrast, the self-trapping of the electronic wavefunctions of S1 and T1(T1†) mostly follows their lattice distortions. Geometry relaxation plays an important role in the localization of the S1 and T1† excitons owing to the non-variational construction of the excited state wavefunction. While, mean-field calculated P+, P- and T1 states are always spatially localized even in ground state S0 geometry. Polaron P+ and P- formation is signified by the presence of the localized states for the hole or the electron deep inside the HOMO-LUMO gap of the oligomer as a result of the orbital stabilization at the LC-wPBE level. The broadening of the HOMO-LUMO band gap for the T1 exciton compared to the charged states is associated with the inverted bond length alternation observed at this level. The molecular orbital energetics are investigated to identify the relationships between state localization and the corresponding orbital structure.
In Chapter 7, we investigate the effect of various conformational defects of trans and cis nature on the energetics and localization of the charged P+ and P- excitations in PPV and MEH-PPV. We observe that the extent of self-trapping for P+ and P- polarons is highly sensitive on molecular and structural conformations, and distribution of atomic charges within the polymers. The particle-hole symmetry is broken with the introduction of trans defects and inclusion of the polarizable environment in consistent with experiment. The differences in the behavior of PPV and MEH-PPV is rationalized based on their orbital energetics and atomic charge distributions. We show these isomeric defects influence the behavior and drift mobilities of the charge carriers in substituted PPVs.Ph.D.
Doctorate
Physics
Sciences
Physics
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Scheid, Philippe. "Investigation of light–induced ultrafast magnetization dynamics using ab initio methods." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0166.
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Cette thèse commence par une revue de l’état actuel de l’expérimentation et de la théorie liées à la désaimantation ultrarapide induite par de la lumière, ainsi qu'au retournement tout optique dépendant de l'hélicité. Ceci est suivi d’un aperçu de la théorie de la fonctionnelle de la densité, sur laquelle repose la plupart des travaux rapportés par la suite. La première partie des résultats concerne l’étude de l’effet d’une élévation de la température électronique sur les propriétés de la matière aimantée, et plus précisément Ni, Co, Fe et FePt. Nous montrons que le moment magnétique de chaque atome disparaı̂t à la température de Stoner, et que, de manière plus générale ce phénomène impacte l’énergie électronique et la chaleur spécifique, même à basse température électronique. Ensuite, nous montrons que lors d’une augmentation de la température électronique, l’échange interatomique d’Heisenberg, responsable de l’ordre magnétique, diminue. En utilisant l’équation de Landau–Lifshitz–Gilbert atomistique, nous démontrons que cette diminution est suffisante pour induire une forte réduction de l’aimantation moyenne en créant des excitations transversales. La deuxième partie des résultats concerne l’origine de la dépendante en l’hélicité de la dynamique induite par la lumière. Alors que la littérature l’attribue principalement à l’effet Faraday inverse, nous soutenons qu’un autre phénomène, se produisant lors de l’absorption de la lumière, peut rendre compte de la dynamique expérimentale. En effet, lorsque la lumière est absorbée et que les électrons sont excités, le couplage spin–orbite permet la modification de l’état de spin. Il en résulte un changement de la valeur des moments magnétiques atomiques, persistant même après la disparition de la lumière, par opposition à l’effet Faraday inverse. Ensuite, en utilisant la théorie de la fonctionnelle de la densité dépendante du temps, nous calculons la dynamique de l’aimantation induite par de véritables impulsions femtosecondes polarisées circulairement dans le domaine optique et XUV. Dans les deux cas, la dynamique est dépendante de l’hélicité. Cette caractéristique est largement amplifiée dans le régime XUV impliquant les états de semi–coeur 3p. Enfin, nous comparons le rôle relatif de l’effet Faraday inverse et de l’aimantation induite lors de l’absorption de la lumière et montrons que cette dernière joue un rôle prépondérant, surtout après la disparition de la lumière et en régime XUVThis thesis begins with a review of the current experimental and theoretical state of the art related to the light-induced ultrafast demagnetization and the all-optical helicity-dependent switching. This is followed by an overview of density functional theory, upon which relies most of the work reported thereafter. The first set of results concerns the ab initio study of the effect of a rise in the electronic temperature on the magnetized matter properties, and more specifically Fe, Co, Ni and FePt. We show that the magnetic moment carried by each atom disappears at the so–called Stoner temperature, and that this phenomenon impacts the electronic energy and specific heat, even at low electronic temperature. Then, we show that upon an increase in the electronic temperature, the interatomic Heisenberg exchange, which is responsible for the magnetic ordering, decreases. Using the atomistic Langevin Landau–Lifshitz–Gilbert equation, we demonstrate that this decrease is enough to induce a large reduction of the average magnetization by creating transversal excitations. The second set of results regards the origin of the helicity–dependent light–induced dynamics. While the literature attributes it mainly to the inverse Faraday effect, we argue that another and novel phenomenon, which occurs during the absorption of the light, may be more suited to account for the experimental dynamics. Indeed, using the Fermi golden rule and ground state density functional theory calculations in Fe, Co, Ni and FePt, we show that, as the light is absorbed and electrons are excited, concurrently to the increase of the electronic energy, the spin–state is also changed in presence of spin–orbit coupling. This results in a difference in the value of the atomic magnetic moments, persisting even after the light is gone, as opposed to the inverse Faraday effect. Then, using real–time time–dependent density functional theory, we compute the magnetization dynamics induced by real optical and XUV femtosecond circularly polarized pulses. We show that, in both cases the dynamics is helicity–dependent and that this characteristic is largely amplified in the XUV regime involving the semi–core 3p states. Finally, we compare the relative role of the inverse Faraday effect and the magnetization induced during the absorption of the light and show that the latter plays a prominent role, especially after the light has gone, and in the XUV regime
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Wawire, Cleophas. "Investigation des photocatalystes de Ruthénium à l'échelle Nano." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00768059.
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Le but de cette thèse est la compréhension de pourquoi certains complexes de ruthénium sont soit pasluminescents soit avec un temps de vie très courte de l'état excité. Des calculs de type théorie de lafonctionnelle de la densité (DFT) ou DFT dépendante du temps (TD-DFT) étaient effectués pour cinqcomplexes existants et aussi pour un complexe hypothétique. Selon la théorie de champs de ligand (LFT),la plus proche sont les énergies des états de type transfert de charge métal-ligand (MLCT) à un état de typemétal centré (MC), alors le plus facile est-ce à peupler l'état MC ainsi menant à une dèsexcitation nonradiative de l'état MLCT. Les calculs DFT/TD-DFT s'avéraient suffisants pour reproduire les géométrieset spectres d'absorption expérimentales. Ceci, ensemble avec la technique de densité d'états partielle,permettaient une validation de l'idée fondamentale issue du modèle LFT en confrontant les résultats denos calculs avec les temps de vie mesurés.
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Motornyi, Oleksandr. "Ab initio study of electronic surfaces states and plasmons of gold : role of the spin-orbit coupling and surface geometry." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX116.
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Cette thèse de doctorat est dédiée à l’étude, avec des méthodes de calcul ab initio, desplasmons de surface et des états de surface de surfaces d’or, plate ou comportant desmarches (surface vicinale), par la simulation numérique de spectres de perte d’énergieélectronique (EEL) au moyen de la théorie de la fonctionnelle de la densité (DFT) et de lathéorie de perturbation de la fonctionnelle de la densité dépendant du temps (TDDFPT).L’influence du couplage spin-orbite (CSO) et celle de la géométrie de la surface ont étéétudiées. Dans l’or cristallin, j’ai étudié l’effet des électrons de semicoeur sur les spectresEEL à q = 0. J’ai montré en particulier que pour produire un spectre EEL sur une largegamme de fréquences, de 0 à 60 eV, il est nécessaire de tenir compte des électrons desemicoeur dans le pseudopotentiel, et qu’ils peuvent néanmoins être gelés dans le coeurpour l’étude de la partie basse en énergie du spectre EEL, pour des énergies inférieures à20 eV. J’ai réalisé des développements méthodologiques pour la TDDFPT avec CSO cou-plée à l’emploi de pseudopotentiels ultradoux, qui ont permis l’implémentation pratiquede cette approche dans les algorithmes de Liouville-Lanczos et de Sternheimer. J’ai utiliséavec succès ces approches qui m’ont permis de traiter des systèmes à plusieurs centainesd’atomes. J’ai examiné à nouveau le spectre EEL de l’or cristallin à q = 0, montrant enparticulier les traces d’un plasmon écranté dans le spectre EEL calculé sans inclure leseffets de CSO. J’ai ensuite montré que l’inclusion du CSO a un effet petit mais détectablesur le spectre EEL et le pic de plasmon, donnant un meilleur accord avec l’expérienceà q = 0. J’ai trouvé que la dispersion du plasmon acoustique (PAS) de la surface Au(111) est légèrement modifiée par le CSO, provenant du fait que la structure de bandesest elle-même modifiée par le dédoublement de Rashba de certains niveaux électroniques,dédoublement induit par le CSO. Puis, pour étudier les effets de géométrie, j’ai étudié lessurfaces vicinales (322), (455) et (788) de l’or. J’ai en particulier mené l’étude théoriquedes états électroniques de surface, et analysé l’évolution de l’état de surface de Shockleyentre la surface plate Au(111) et les surfaces ayant des marches dont les terrasses avaientdifférentes largeurs. J’ai montré la transition d’un état de surface résonant pour Au(322)à un état localisé pour Au(455) et pour Au(788), ainsi que le passage d’un état 2D étenduà travers la marche pour Au(322) à un état quasi-1D confiné dans la terrasse de la marchepour Au(455) et pour Au(788). Ces résultats sont en accord avec l’expérience, et avecceux d’un modèle de Kronig-Penney de potentiel périodique. J’ai calculé le spectre EELSpour la surface d’or (455) que j’ai modélisé par une tranche de 5 nm d’or séparée de sesvoisines (répétées périodiquement) par 5 nm de vide. J’ai identifié la signature du plas-mon acoustique de surface. J’ai montré que, pour un moment transféré perpendiculaireà la marche de la surface, la dispersion du PAS n’est pas modifiée par rapport à celle duPAS de la surface plate Au(111) pour q < 0.125 Å −1 . Cependant, pour des valeurs plusgrandes du moment transféré, le pic du PAS a une énergie plus basse que celle du PASde Au(111), montrant les signes du confinement du PAS et suggérant que deux types dePAS peuvent se produire: un plasmon intra(sous)bande, similaire à celui de la surfaceAu(111), et un plasmon inter(sub)band, caractéristique de cette surface vicinaleThe PhD thesis is devoted to the ab initio study of surface plasmons and surface states offlat and vicinal surfaces of Au through the simulation of electron energy loss (EEL) spectraby means of the density functional theory (DFT) and the time-dependent density func-tional perturbation theory (TDDFPT). The influence of the spin-orbit coupling (SOC)and of the surface geometry has been investigated. In bulk Au I have studied the effect ofthe inclusion of semi-core electrons on the EEL spectrum at q = 0 and the plasmon peakposition and intensity. In particular, I have shown that in order to reproduce the EELspectrum on a wide frequency range (0-60 eV) it is important to account for semi-coreelectrons in the pseudopotential although they can be frozen in the core in studies of thelow energy part of the spectrum (below 20 eV). I have made methodological developmentsfor TDDFPT with SOC in the ultrasoft pseudopotential scheme that led to the practicalimplementation of SOC in the Liouville-Lanczos and Sternheimer approaches. I have thensuccessfully applied these approaches that allowed me to model systems with hundreds ofatoms. I have revisited the plasmonic excitations in bulk Au, pointing out that, in partic-ular, one can observe traces of an unscreened s-like bulk plasmon in the EEL spectrum atq = 0 calculated without SOC. I have also demonstrated that SOC has a small but notice-able effect on the Au EEL spectrum and plasmon peak, mainly modifying the unscreeneds-like plasmon peak and thus bringing the calculated spectrum into a better agreementwith experimental results at q = 0. Moreover I have observed that the dispersion ofthe acoustic surface plasmon (ASP) on the Au(111) surface is slightly modified by SOC,because the ASP comes from the surface state that itself is modified by SOC through theRashba splitting. To investigate the effect of geometry I have studied the vicinal (322),(455) and (788) surfaces of Au. In particular I have performed the theoretical study of thesurface states, analyzing the evolution of the Shockley surface state from the flat Au(111)surface towards the surfaces with terraces of different width. I have shown the surfaceresonance-to-surface state transition from (322) to (455) and (788) surfaces. I have shownalso the transition from the average-surface-modulated to the terrace-modulated statefrom (322) to (455) and (788) surfaces, as well as the transition from the extended 2Dstate to the quasi-1D state confined within the terrace. These results are in agreementwith experiments and results obtained with the Kronig-Penney periodic potential model.I have performed the EEL spectrum calculations for the Au(455) surface which I havemodeled with a 5 nm sized slab separated from its periodic neighbors by 5 nm of vacuum.I have identified signatures of the ASP in these spectra, showing that indeed, for the caseof the transferred electron wavevector momentum perpendicular to the step, the ASPdispersion is not changed with respect to the ASP dispersion of the Au(111) surface forq < 0.125 Å −1 . For bigger values of q, however, the ASP peak has a lower energy com-pared to the ASP peak of the Au(111) surface, showing signs of the ASP confinement, andsuggesting that two types of the ASP could occur: an intra(sub)band plasmon, similarto the Au(111) surface plasmon, and an inter(sub)band plasmon, characteristic of thisvicinal surface
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Gong, Yun. "Structure-property relationships of dyes as applied to dye-sensitized solar cells." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/275007.
Full textAbstract:
This work investigates the correlation of structural and photovoltaic properties of dyes used in dye-sensitized solar cells. Experimental methods, including ultraviolet-visible spectroscopy, fluorescence spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy are employed to study optical and electrochemical properties of dye molecules. Computational methods, including density functional theory and time-dependent density functional theory, are used to validate and predict the optical and electronic properties of dye molecules, in their isolated state and once embedded into a working electrode device environment that comprises a dye...TiO2 interface. The results chapters begin with the presentation of a series of quinodimethene dyes that are experimentally validated for their photovoltaic application, and associated computational studies reveal that an inner structural factor - a phenyl ring rotation occurring during the optical excitation process - leads to the competitive photovoltaic device performance of these dyes. Carbazole-based dyes are then systematically studied by computation, especially considering charge transfer paths and binding modes of these dyes on a titania surface. The theoretical models for the basic building block of this chemical family of dyes, known as MK-44, successfully support and explain structural discoveries from X-ray diffraction and reflectometry that impact of their function. A benzothiadiazole-based dye, RK-1, is then systematically studied by both experimental and computational methods, and the results show that the π-bridge composed of thiophene, benzothiadiazole and benzene rings leads to excellent charge separation; and the rotation of these rings during the optical excitation process may well be consistent with the fluorescence spectrum. Finally, the well-known ruthenium-based dyes are theoretically studied to determine the properties of different ligands connected to the metal core of the complex. Conformations with different NCS ligands are calculated in terms of energy and explain well the corresponding results from X-ray diffraction. Acid-base properties of carboxyl groups connected to pyridine ligands in N3 and N749 are theoretically calculated based on thermodynamics and density functional theory. Implicit and explicit models are both adopted to predict these acid dissociative constant values, which are generally in a good agreement with the reported experimental data. The thesis concludes with conclusions and a future outlook.