Relevant bibliographies by topics / LCAO (Linear combination of Atomic Orbitals)

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters

Academic literature on the topic 'LCAO (Linear combination of Atomic Orbitals)'

Author: Grafiati
Published: 4 June 2021
Last updated: 17 February 2022

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'LCAO (Linear combination of Atomic Orbitals).'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "LCAO (Linear combination of Atomic Orbitals)"

1

Custodio, Rogério, and Nelson Henrique Morgon. "Método LCAO." Revista Chemkeys, no. 3 (September 17, 2018): 1–8. http://dx.doi.org/10.20396/chemkeys.v0i3.9639.

Full text
Abstract:
Orbitais atômicos e moleculares podem ser obtidos como uma combinação linear de funções de base. Este modelo ficou conhecido como método da combinação linear de orbitais atômicos (do inglês: Linear Combination of Atomic Orbitals), sendo uma das técnicas mais utilizadas para o cálculo de propriedades eletrônicas de átomos, moléculas, etc., por métodos quânticos. Neste texto serão abordados alguns dos aspectos fundamentais para o cálculo de propriedades eletrônicas através do método denominado Hartree-Fock-Roothaan, que corresponde à aplicação da combinação linear de orbitais atômicos usando o modelo Hartree-Fock.
APA, Harvard, Vancouver, ISO, and other styles
2

Nakhaee, M., M. Yagmurcukardes, S. A. Ketabi, and F. M. Peeters. "Single-layer structures of a100- and b010-Gallenene: a tight-binding approach." Physical Chemistry Chemical Physics 21, no. 28 (2019): 15798–804. http://dx.doi.org/10.1039/c9cp02515d.

Full text
Abstract:
Using the simplified linear combination of atomic orbitals (LCAO) method in combination with ab initio calculations, we construct a tight-binding (TB) model for two different crystal structures of monolayer gallium: a100- and b010-Gallenene.
APA, Harvard, Vancouver, ISO, and other styles
3

MISHONOV, T. M., J. P. WALLINGTON, E. S. PENEV, and J. O. INDEKEU. "REDUCED PAIRING HAMILTONIAN FOR INTERATOMIC TWO-ELECTRON EXCHANGE IN LAYERED CUPRATES." Modern Physics Letters B 16, no. 19 (August 20, 2002): 693–99. http://dx.doi.org/10.1142/s0217984902004160.

Full text
Abstract:
A detailed Linear Combination of Atomic Orbitals (LCAO) tight-binding model is developed for the layered High-Temperature Superconductor (HTSC) cuprates. The band structure of these materials is described using a σ-band Hamiltonian employing Cu 4s, Cu 3dx2 - y2, O 2px and O 2py atomic orbitals. The Fermi level and the shape of the resulting Fermi surface are fitted to recent Angle Resolved Photon Emission Spectroscopy (ARPES) data to realistically determine the dispersion in the conduction band. Electron-electron interactions and, ultimately, Cooper pairing are obtained by introducing a Heitler–London, two-electron exchange between adjacent orbitals within the CuO 2 plane. Finally, using the LCAO wavefunctions determined by the band structure fit, the Bardeen–Cooper–Schrieffer (BCS) type kernel is derived for interatomic exchange.
APA, Harvard, Vancouver, ISO, and other styles
4

Weng, Xudong, O. F. Sankey, and Peter Rez. "Ab initio band theory approach to electron energy loss near edge structures." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 506–7. http://dx.doi.org/10.1017/s0424820100104595.

Full text
Abstract:
Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.
APA, Harvard, Vancouver, ISO, and other styles
5

Mantela, Marilena, Constantinos Simserides, and Rosa Di Felice. "LCAO Electronic Structure of Nucleic Acid Bases and Other Heterocycles and Transfer Integrals in B-DNA, Including Structural Variability." Materials 14, no. 17 (August 30, 2021): 4930. http://dx.doi.org/10.3390/ma14174930.

Full text
Abstract:
To describe the molecular electronic structure of nucleic acid bases and other heterocycles, we employ the Linear Combination of Atomic Orbitals (LCAO) method, considering the molecular wave function as a linear combination of all valence orbitals, i.e., 2s, 2px, 2py, 2pz orbitals for C, N, and O atoms and 1s orbital for H atoms. Regarding the diagonal matrix elements (also known as on-site energies), we introduce a novel parameterization. For the non-diagonal matrix elements referring to neighboring atoms, we employ the Slater–Koster two-center interaction transfer integrals. We use Harrison-type expressions with factors slightly modified relative to the original. We compare our LCAO predictions for the ionization and excitation energies of heterocycles with those obtained from Ionization Potential Equation of Motion Coupled Cluster with Singles and Doubles (IP-EOMCCSD)/aug-cc-pVDZ level of theory and Completely Normalized Equation of Motion Coupled Cluster with Singles, Doubles, and non-iterative Triples (CR-EOMCCSD(T))/aug-cc-pVDZ level of theory, respectively, (vertical values), as well as with available experimental data. Similarly, we calculate the transfer integrals between subsequent base pairs, to be used for a Tight-Binding (TB) wire model description of charge transfer and transport along ideal or deformed B-DNA. Taking into account all valence orbitals, we are in the position to treat deflection from the planar geometry, e.g., DNA structural variability, a task impossible for the plane Hückel approach (i.e., using only 2pz orbitals). We show the effects of structural deformations utilizing a 20mer evolved by Molecular Dynamics.
APA, Harvard, Vancouver, ISO, and other styles
6

Kaledin, Alexey L., Craig L. Hill, Tianquan Lian, and Djamaladdin G. Musaev. "A bulk adjusted linear combination of atomic orbitals (BA-LCAO) approach for nanoparticles." Journal of Computational Chemistry 40, no. 1 (October 3, 2018): 212–21. http://dx.doi.org/10.1002/jcc.25373.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Hamouda, Samir Ahmed. "Gamma-Ray Compton Spectroscopy for Determination of Electron Momentum Distributions in Iron." Advanced Materials Research 815 (October 2013): 8–12. http://dx.doi.org/10.4028/www.scientific.net/amr.815.8.

Full text
Abstract:
Compton profile measurement of iron polycrystalline sample has been performed with 662 keV γ-radiation from a caesium-137 source. The spectrometer calibration and data corrections for the high energy experiment are discussed. The data are compared with the augmented-plane-wave (APW) and linear combination of atomic orbitals (LCAO) band theoretical Compton profiles of iron. Both theoretical predictions show the band theories overestimate the momentum density at low momenta and underestimate it at intermediate momenta.
APA, Harvard, Vancouver, ISO, and other styles
8

Craig, BL, and PV Smith. "Parametrisation of the LCAO Bandstructure of BCC Transition Metals." Australian Journal of Physics 41, no. 6 (1988): 797. http://dx.doi.org/10.1071/ph880797.

Full text
Abstract:
In this paper we present a direct parameter fitting scheme appropriate to a linear combination of atomic orbitals (LCAO) model� Hamiltonian representation of the BCC transition metals incorporating first and second neighbour interactions. Explicit expressions are given for the one-electron eigenvalues at all of the important symmetry points of the BCC Brillouin zone. This direct parameter fitting scheme is shown to produce an excellent representation of the bandstructure of paramagnetic iron, and yields parameter values little different from those obtained from a full least-squares optimisation of the LCAO model Hamiltonian bandstructure. The extension of this scheme to include more distant interactions, and relativistic and spin-orbit effects, is also discussed.
APA, Harvard, Vancouver, ISO, and other styles
9

Biczó, G. "On the self-consistent-field linear combination of atomic orbitals for bounded crystal orbitals (SCF-LCAO-BCO) method." Journal of Molecular Structure: THEOCHEM 188, no. 3-4 (August 1989): 429–39. http://dx.doi.org/10.1016/0166-1280(89)85125-5.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Masuda-Jindo, K., V. K. Tewary, and Robb Thomson. "Atomic theory of fracture of brittle materials: Application to covalent semiconductors." Journal of Materials Research 6, no. 7 (July 1991): 1553–66. http://dx.doi.org/10.1557/jmr.1991.1553.

Full text
Abstract:
Using the lattice Green's function approach and LCAO (linear combination of atomic orbitals) electron theory, we investigate the atomistic configuration and lattice trapping of cracks in Si. The LCAO electron theory coupled to second order perturbation theory (SOP) has been used to derive explicit expressions for the bond breaking nonlinear forces between Si atoms. We calculate the cracked lattice Green's functions for a crack on the (111) plane and lying in the (110) direction. With the nonlinear forces acting in a cohesive region near the crack tips, the crack structure is then calculated. The calculated structure possesses a crack opening at the Griffith load which should allow penetration of typical external molecules to the crack tip at the Griffith loading. Other consequences for chemical reactions at the crack tip are discussed in the light of these results. The lattice trapping is low, only a few percent of the Griffith load.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "LCAO (Linear combination of Atomic Orbitals)"

1

Sapet, Christophe. "Modélisation par la méthode LCAO empirique de la structure électronique : les surfaces propres ou oxydées du cuivre." Châtenay-Malabry, Ecole centrale de Paris, 2003. http://www.theses.fr/2003ECAP0889.

Full text
Abstract:
Les trois surfaces de plus bas indices de Miller du Cuivre ainsi que la reconstruction de la surface (110) suite à l'adsorption d'oxygène atomique ont été étudiées dans cette thèse. Il a fallu pour cela développer les outils nécessaires d'une part à la modélisation de la structure des bandes d'énergie de ces surfaces et d'autre part à l'ajustement des bandes calculées sur des données expérimentales obtenues par photo-émission directe et inverse. Cela a été réalisé en combinant la méthode LCAO empirique d'interpolation de calculs de bandes d'énergie des solides et un programme de minimisation de fonctions à plusieurs paramètres. Dans la première étape, qui a consisté à modéliser un cristal massif ainsi que les principales surfaces propres, nous avons inclus dans le processus d'ajustement des données expérimentales issues de mesures sur la surface (110), ce qui nous a permis d'obtenir un seul ensemble de paramètres décrivant les interactions des atomes dans le Cuivre massif et applicable aux études des surfaces. Cet ensemble de paramètres a donné une structure de bandes du volume et des surfaces en accord très poussé avec les données expérimentales, ce qui n'existait pas jusqu'à présent dans la littérature. Nous avons ensuite établi un deuxième ensemble de paramètres afin de prendre en compte les interactions d'atomes d'oxygène avec un substrat de Cuivre, ce dernier étant décrit par les paramètres précédemment obtenus. Nous avons ainsi pu modéliser la structure des bandes de la surface (110) oxydée dans ses plus fins détails, et notamment la dispersion et la symétrie des états anti-liants de l'oxygène, ce qui n'avait jamais été réalisé auparavant ni dans le cadre d'une modélisation LCAO, ni dans le cadre de calculs ab-initio. Les applications de ces calculs sont multiples, et tous les travaux menés pour étudier le cristal de Cuivre et ses principales surfaces peuvent être reconduits pour d'autres métaux de transition.
APA, Harvard, Vancouver, ISO, and other styles
2

Schmidt, Torsten. "Saturated bonds and anomalous electronic transport in transition-metal aluminides." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601769.

Full text
Abstract:
Diese Arbeit beschäftigt sich mit den besonderen elektronischen Eigenschaften der Übergangsmetall-Aluminide. In Anlehnung an die Quasikristalle und ihre Approximanten zeigt sich, dass selbst Materialien mit kleinen Einheitszellen die gleichen überraschenden Effekte aufweisen. So gibt es unter den Übergangsmetall-Aluminiden auch semimetallische und halbleitende Verbindungen, auch wenn sie aus klassisch-metallischen Komponenten wie Fe, Al oder Cr bestehen. Diese Eigenschaften sind außerdem mit einem tiefen Pseudogap bzw. Gap in der Zustandsdichte und starken kovalenten Bindungen gekoppelt. Bindungen werden im Rahmen dieser Arbeit durch zwei wesentliche Eigenschaften beschrieben. Erstens durch die Bindungsladung und zweitens durch die energetische Auswirkung der Bindung. Es ergibt sich, dass im Fall halbleitender Übergangsmetall-Aluminide zum einen eine Sättigung von bestimmten Bindungen, wie auch ein bindungs-antibindungs-Wechsel bei der Fermi-Energie vorliegt. Mit der Analyse der Nahordnung in Form der sogenannten lokalen Koordinationspolyeder ist es gelungen, eine einfache Regel für Halbleiter aufzustellen, die Fünffachkoordination für Al. Diese Regel besagt, dass Aluminium-Atome mit ihren drei Valenzelektronen nicht in der Lage sind, mehr als fünf gesättigte Bindungen zu ihren nächsten Übergangsmetall-Nachbarn aufzubauen. In exzellenter Übereinstimmung mit den in Annahme gleichartiger Bindungen theoretisch vorhergesagten Bindungswinkel ergibt sich, dass alle binären Übergangs-Aluminid-Halbleiter für die Al-Atome die gleiche Nahordnung aufweisen. Typische Werte für spezifische Widerstände der untersuchten Materialien bei Raumtemperatur liegen im Bereich von einigen 100µOhm cm, was weit größer ist als einige 10µOhm cm wie im Fall der unlegierten Metalle. Überraschend ist außerdem eine hohe Transportanisotropie mit einem Verhältnis der spezifischen Widerstände bis zu 3.0. Eine wesentliche Errungenschaft der Arbeit kann in der Verknüpfung der Eigenschaft des elektronischen Transports und der Bindungseigenschaften gesehen werden. Die geringen Leitfähigkeiten konnten durch geringe Werte in der Zustandsdichte (DOS) und einem bei gleicher Energie stattfindenden bindungs-antibindungs-Wechsel erklärt werden.
APA, Harvard, Vancouver, ISO, and other styles
3

Schmidt, Torsten. "Saturated bonds and anomalous electronic transport in transition-metal aluminides." Doctoral thesis, 2005. https://monarch.qucosa.de/id/qucosa%3A18614.

Full text
Abstract:
Diese Arbeit beschäftigt sich mit den besonderen elektronischen Eigenschaften der Übergangsmetall-Aluminide. In Anlehnung an die Quasikristalle und ihre Approximanten zeigt sich, dass selbst Materialien mit kleinen Einheitszellen die gleichen überraschenden Effekte aufweisen. So gibt es unter den Übergangsmetall-Aluminiden auch semimetallische und halbleitende Verbindungen, auch wenn sie aus klassisch-metallischen Komponenten wie Fe, Al oder Cr bestehen. Diese Eigenschaften sind außerdem mit einem tiefen Pseudogap bzw. Gap in der Zustandsdichte und starken kovalenten Bindungen gekoppelt. Bindungen werden im Rahmen dieser Arbeit durch zwei wesentliche Eigenschaften beschrieben. Erstens durch die Bindungsladung und zweitens durch die energetische Auswirkung der Bindung. Es ergibt sich, dass im Fall halbleitender Übergangsmetall-Aluminide zum einen eine Sättigung von bestimmten Bindungen, wie auch ein bindungs-antibindungs-Wechsel bei der Fermi-Energie vorliegt. Mit der Analyse der Nahordnung in Form der sogenannten lokalen Koordinationspolyeder ist es gelungen, eine einfache Regel für Halbleiter aufzustellen, die Fünffachkoordination für Al. Diese Regel besagt, dass Aluminium-Atome mit ihren drei Valenzelektronen nicht in der Lage sind, mehr als fünf gesättigte Bindungen zu ihren nächsten Übergangsmetall-Nachbarn aufzubauen. In exzellenter Übereinstimmung mit den in Annahme gleichartiger Bindungen theoretisch vorhergesagten Bindungswinkel ergibt sich, dass alle binären Übergangs-Aluminid-Halbleiter für die Al-Atome die gleiche Nahordnung aufweisen. Typische Werte für spezifische Widerstände der untersuchten Materialien bei Raumtemperatur liegen im Bereich von einigen 100µOhm cm, was weit größer ist als einige 10µOhm cm wie im Fall der unlegierten Metalle. Überraschend ist außerdem eine hohe Transportanisotropie mit einem Verhältnis der spezifischen Widerstände bis zu 3.0. Eine wesentliche Errungenschaft der Arbeit kann in der Verknüpfung der Eigenschaft des elektronischen Transports und der Bindungseigenschaften gesehen werden. Die geringen Leitfähigkeiten konnten durch geringe Werte in der Zustandsdichte (DOS) und einem bei gleicher Energie stattfindenden bindungs-antibindungs-Wechsel erklärt werden.
APA, Harvard, Vancouver, ISO, and other styles

Books on the topic "LCAO (Linear combination of Atomic Orbitals)"

1

Electronic Structure Methods For Complex Materials The Orthogonalized Linear Combination Of Atomic Orbitals. Oxford University Press, USA, 2012.

Find full text
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "LCAO (Linear combination of Atomic Orbitals)"

1

Clark, Tim, and Rainer Koch. "Linear Combination of Atomic Orbitals." In The Chemist’s Electronic Book of Orbitals, 5–22. Berlin, Heidelberg: Springer Berlin Heidelberg, 1999. http://dx.doi.org/10.1007/978-3-662-13150-3_2.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Causà, Mauro. "Numerical Integration in Density Functional Methods with Linear Combination of Atomic Orbitals." In Lecture Notes in Chemistry, 91–100. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61478-1_5.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Brener, N. E., J. Callaway, and J. M. Tyler. "BNDPKG2: A Linear Combination of Gaussian Orbitals (LCGO) Band Structure Program for Cubic Crystals With One Atom Per Unit Cell." In Modem Techniques in Computational Chemistry: MOTECC-91, 773–91. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3032-5_18.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Brener, N. E., J. Callaway, and J. M. Tyler. "BNDPKG2: A Linear Combination of Gaussian Orbitals (LCGO) Band Structure Program for Cubic Crystals With One Atom Per Unit Cell." In Modern Techniques in Computational Chemistry: MOTECC™-90, 785–803. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-2219-8_16.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Autschbach, Jochen. "From Atomic Orbitals to Molecular Orbitals and Chemical Bonds." In Quantum Theory for Chemical Applications, 150–87. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190920807.003.0009.

Full text
Abstract:
It is shown how an aufbau principle for atoms arises from the Hartree-Fock (HF) treatment with increasing numbers of electrons. The Slater screening rules are introduced. The HF equations for general molecules are not separable in the spatial variables. This requires another approximation, such as the linear combination of atomic orbitals (LCAO) molecular orbital method. The orbitals of molecules are represented in a basis set of known functions, for example atomic orbital (AO)-like functions or plane waves. The HF equation then becomes a generalized matrix pseudo-eigenvalue problem. Solutions are obtained for the hydrogen molecule ion and H2 with a minimal AO basis. The Slater rule for 1s shells is rationalized via the optimal exponent in a minimal 1s basis. The nature of the chemical bond, and specifically the role of the kinetic energy in covalent bonding, are discussed in details with the example of the hydrogen molecule ion.
APA, Harvard, Vancouver, ISO, and other styles
6

Autschbach, Jochen. "Band Structure Theory for Extended Systems." In Quantum Theory for Chemical Applications, 246–78. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190920807.003.0013.

Full text
Abstract:
The electronic structure of infinite periodic systems (crystals) is treated with band structure theory, replacing molecular orbitals by crystal orbitals. The chapter starts out by introducing the electron gas and definitions of the Fermi momentum, the Fermi energy, and the density of states (DOS). A periodic linear combination of atomic orbitals (LCAO) type treatment of an infinite periodic system is facilitated by the construction of Bloch functions. The notions of energy band and band gap are discussed with band structure concepts, using the approximations made in Huckel theory (chapter 12). One, two, and three-dimensional crystal lattices and the associated reciprocal lattices are introduced. The band structures of sodium metal, boron nitride, silicon, and graphite, are discussed as examples of metals, insulators, semi-conductors, and semi-metals, respectively. The chapter concludes with a brief discussion of the projected DOS and measures to determine bonding or antibonding interactions between atoms in a crystal.
APA, Harvard, Vancouver, ISO, and other styles
7

Dyall, Kenneth G., and Knut Faegri. "One-Electron Atoms." In Introduction to Relativistic Quantum Chemistry. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195140866.003.0012.

Full text
Abstract:
The development of quantum chemistry, that is, the solution of the Schrödinger equation for molecules, is almost exclusively founded on the expansion of the molecular electronic wave function as a linear combination of atom-centered functions, or atomic orbitals—the LCAO approximation. These orbitals are usually built up out of some set of basis functions. The properties of the atomic functions at large and small distances from the nucleus determines to a large extent what characteristics the basis functions must have, and for this purpose it is sufficient to examine the properties of the hydrogenic solutions to the Schrödinger equation. If we are to do the same for relativistic quantum chemistry, we should first examine the properties of the atomic solutions to determine what kind of basis functions would be appropriate. However, the atomic solutions of the Dirac equation provide more than merely a guide to the choice of basis functions. The atoms in a molecule retain their atomic identities to a very large extent, and the modifications caused by the molecular field are quite small for most properties. In order to arrive at a satisfactory description of the relativistic effects in molecules, we must first of all be able to treat these effects at the atomic level. The insight gained into the effects of relativity on atomic structure is therefore a necessary and useful starting point for relativistic quantum chemistry. As in the nonrelativistic case, most of the salient features of the atomic systems are exposed in the treatment of the simplest of these, the hydrogen-like one-electron atoms. In Hartree atomic units the time-independent Dirac equation yields the coupled equations where we have shifted the energy by −mc2 (with m = 1), as discussed in section 4.6. We will use this shifted energy scale for the rest of the book unless otherwise explicitly indicated. V is here a scalar, central potential.
APA, Harvard, Vancouver, ISO, and other styles
8

Autschbach, Jochen. "Recap: Molecular Orbitals and Common Misconceptions." In Quantum Theory for Chemical Applications, 217–30. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190920807.003.0011.

Full text
Abstract:
This chapter recapitulates the series of approximations that lead to the commonly used description of the electronic structure of molecules in terms of molecular orbitals (MOs), which in turn are usually expressed as linear combination of atomic orbital-like basis functions. Next, a number of common misconceptions about orbitals are discussed, such that the reader is aware of not only what electron orbitals are but also what they are not.
APA, Harvard, Vancouver, ISO, and other styles
9

Forrest, Stephen R. "Optical properties of organic semiconductors." In Organic Electronics, 74–170. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198529729.003.0003.

Full text
Abstract:
Organic semiconductors are often called excitonic materials since their optical properties derive from the photogeneration of excitons, that is, bound electron–hole pairs. Organic excitons are either Frenkel or charge-transfer-like with binding energies of 0.5–1.0 eV, making them stable at room temperature. This chapter describes the fundamental optical properties of organics, starting with those of individual molecules, and then building the solid from pairs of molecules (dimers) and oligomers. Theoretical approaches to describe optical properties start by introducing the Born–Oppenheimer approximation and the Franck–Condon principle. Calculational approaches to understanding optical characteristics based on the linear combination of atomic orbitals are described. Both theory and experimental observation of optical phenomena are discussed in detail. Also, electron spin, spin–orbit coupling, fluorescence, and phosphorescence are quantitatively described. Finally, long and short range energy transfer, exciton diffusion, and annihilation processes ae described.
APA, Harvard, Vancouver, ISO, and other styles
10

Wesolowski, Tomasz Adam, and Jacques Weber. "Applications of Density Functional Theory to Biological Systems." In Molecular Orbital Calculations for Biological Systems. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195098730.003.0009.

Full text
Abstract:
The term biological systems may be used in reference to a wide class of polyatomic systems. They can be defined as minimal functional units which perform specific biological functions: enzymatic reactions, transport across membranes, or photosynthesis. At present, such systems as a whole are not amenable to quantum-chemistry studies because of their large size. The smallest enzymes are built of few thousands of atoms (e.g., lysozyme consists of 129 amino-acid subunits), the smallest nucleic acids are of similar size (e.g., t-RNA molecules consist of about 80 nucleotide subunits), whereas biological membranes are even larger and include different biological macromolecules embedded in a phospholipide medium. On the other hand, a common-sense definition of the term biological systems refers to any chemical molecule or molecular complex which is involved in biological or biochemical processes. The latter definition, which will be used throughout this review, covers not only complete functional units performing biological functions but also fragments of such units. Theoretical studies have provided data on properties of such fragments and have helped understanding of the biological processes at the molecular level. Depending upon the size of such fragments, they can be studied by means of various quantum-chemical methods. Molecular systems of up to a few thousands of atoms can be studied using semi-empirical methods. For the Hartree-Fock or Kohn-Sham density functional theory (DFT) calculations, the current size limit is a few hundreds of atoms. (Throughout the text, Hartree-Fock refers to ab initio Self-Consistent Field calculations using the approximation of linear combination of atomic orbitals.) When the desired accuracy requires the calculation of electron correlation at the ab initio level, only systems containing no more than few tens of atoms can be treated. Therefore, a theoretician aiming at the elucidation of biological processes by quantum-mechanical calculations faces two crucial issues. The first one is the selection of a fragment for modeling at the quantum-mechanical level. The second one is the assessment of the effects associated with parts of the system which cannot be modeled at the quantum-mechanical level. In this review, the DFT studies of biological systems are divided into two groups corresponding to different ways of addressing the second aforementioned issue.
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'LCAO (Linear combination of Atomic Orbitals)' for particular source types:
Journal articles
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography