Journal articles: 'RT-TDDFT'

1

Andermatt, Samuel, Mohammad Hossein Bani-Hashemian, Fabian Ducry, Sascha Brück, Sergiu Clima, Geoffrey Pourtois, Joost VandeVondele, and Mathieu Luisier. "Microcanonical RT-TDDFT simulations of realistically extended devices." Journal of Chemical Physics 149, no. 12 (September 28, 2018): 124701. http://dx.doi.org/10.1063/1.5040048.

Full text

APA, Harvard, Vancouver, ISO, and other styles

2

Peng, Wei-Tao, and Jeng-Da Chai. "Assessment of asymptotically corrected model potentials for charge-transfer-like excitations in oligoacenes." Phys. Chem. Chem. Phys. 16, no. 39 (2014): 21564–69. http://dx.doi.org/10.1039/c4cp02946a.

Full text

Abstract:

Absorption spectra of 5-acene calculated using various functionals in RT-TDDFT. The subfigures (left top: LDA; left bottom: PBE; right: LB94) show the spectra close to the position of the ¹L_a and ¹L_b peaks, where the corresponding LR-TDDFT results are marked with the red lines.

APA, Harvard, Vancouver, ISO, and other styles

3

Li, Xiaojuan, Xinlu Cheng, and Hong Zhang. "Ab initio dynamics simulation of laser-induced photodissociation of phenol." Physical Chemistry Chemical Physics 23, no. 22 (2021): 12718–30. http://dx.doi.org/10.1039/d1cp00290b.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Yang, Junjie, Zheng Pei, Jingheng Deng, Yuezhi Mao, Qin Wu, Zhibo Yang, Bin Wang, Christine M. Aikens, Wanzhen Liang, and Yihan Shao. "Analysis and visualization of energy densities. I. Insights from real-time time-dependent density functional theory simulations." Physical Chemistry Chemical Physics 22, no. 46 (2020): 26838–51. http://dx.doi.org/10.1039/d0cp04206d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Roy, Sima, Shuvam Pramanik, Tapas Ghorui, and Kausikisankar Pramanik. "Insight into luminescent bisazoaromatic CNN pincer palladacycle: synthesis, structure, electrochemistry and some catalytic applications in C–C coupling." RSC Advances 5, no. 29 (2015): 22544–59. http://dx.doi.org/10.1039/c4ra16584e.

Full text

Abstract:

The 2-(phenylazo)azobenzene furnished novel palladacycles in excellent yield, which showed luminescence at rt and catalytic activity. The optoelectronic and electrochemical responses were substantiated with DFT and TDDFT.

APA, Harvard, Vancouver, ISO, and other styles

6

Mokkath, Junais Habeeb. "Localized surface plasmon resonances of a metal nanoring." Physical Chemistry Chemical Physics 22, no. 41 (2020): 23878–85. http://dx.doi.org/10.1039/d0cp04216a.

Full text

Abstract:

Using the linear combination of atomic orbitals real-time-propagation rt-TDDFT technique and transition contribution maps, we study the optical and plasmonic features of a metal nanoring made up of sodium atoms.

APA, Harvard, Vancouver, ISO, and other styles

7

Bowman, David N., Jason C. Asher, Sean A. Fischer, Christopher J. Cramer, and Niranjan Govind. "Excited-state absorption in tetrapyridyl porphyrins: comparing real-time and quadratic-response time-dependent density functional theory." Phys. Chem. Chem. Phys. 19, no. 40 (2017): 27452–62. http://dx.doi.org/10.1039/c7cp04567k.

Full text

Abstract:

Three meso-substituted tetrapyridyl porphyrins (free base, Ni(ii), and Cu(ii)) were investigated for their optical limiting (OL) capabilities using real-time (RT-), linear-response (LR-), and quadratic-response (QR-) time-dependent density functional theory (TDDFT) methods.

APA, Harvard, Vancouver, ISO, and other styles

8

Li, Tao E., and Sharon Hammes-Schiffer. "Electronic Born–Oppenheimer approximation in nuclear-electronic orbital dynamics." Journal of Chemical Physics 158, no. 11 (March 21, 2023): 114118. http://dx.doi.org/10.1063/5.0142007.

Full text

Abstract:

Within the nuclear-electronic orbital (NEO) framework, the real-time NEO time-dependent density functional theory (RT-NEO-TDDFT) approach enables the simulation of coupled electronic-nuclear dynamics. In this approach, the electrons and quantum nuclei are propagated in time on the same footing. A relatively small time step is required to propagate the much faster electronic dynamics, thereby prohibiting the simulation of long-time nuclear quantum dynamics. Herein, the electronic Born–Oppenheimer (BO) approximation within the NEO framework is presented. In this approach, the electronic density is quenched to the ground state at each time step, and the real-time nuclear quantum dynamics is propagated on an instantaneous electronic ground state defined by both the classical nuclear geometry and the nonequilibrium quantum nuclear density. Because the electronic dynamics is no longer propagated, this approximation enables the use of an order-of-magnitude larger time step, thus greatly reducing the computational cost. Moreover, invoking the electronic BO approximation also fixes the unphysical asymmetric Rabi splitting observed in previous semiclassical RT-NEO-TDDFT simulations of vibrational polaritons even for small Rabi splitting, instead yielding a stable, symmetric Rabi splitting. For the intramolecular proton transfer in malonaldehyde, both RT-NEO-Ehrenfest dynamics and its BO counterpart can describe proton delocalization during the real-time nuclear quantum dynamics. Thus, the BO RT-NEO approach provides the foundation for a wide range of chemical and biological applications.

APA, Harvard, Vancouver, ISO, and other styles

9

Tassi, M., A. Morphis, K. Lambropoulos, C. Simserides, and Bernardo Spagnolo. "RT-TDDFT study of hole oscillations in B-DNA monomers and dimers." Cogent Physics 4, no. 1 (January 1, 2017): 1361077. http://dx.doi.org/10.1080/23311940.2017.1361077.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Simserides, Constantinos, Andreas Morphis, and Konstantinos Lambropoulos. "Hole Transfer in Open Carbynes." Materials 13, no. 18 (September 8, 2020): 3979. http://dx.doi.org/10.3390/ma13183979.

Full text

Abstract:

We investigate hole transfer in open carbynes, i.e., carbon atomic nanowires, using Real-Time Time-Dependent Density Functional Theory (RT-TDDFT). The nanowire is made of N carbon atoms. We use the functional B3LYP and the basis sets 3-21G, 6-31G*, cc-pVDZ, cc-pVTZ, cc-pVQZ. We also utilize a few Tight-Binding (TB) wire models, a very simple model with all sites equivalent and transfer integrals given by the Harrison ppπ expression (TBI) as well as a model with modified initial and final sites (TBImod) to take into account the presence of one or two or three hydrogen atoms at the edge sites. To achieve similar site occupations in cumulenes with those obtained by converged RT-TDDFT, TBImod is sufficient. However, to achieve similar frequency content of charge and dipole moment oscillations and similar coherent transfer rates, the TBImod transfer integrals have to be multiplied by a factor of four (TBImodt4times). An explanation for this is given. Full geometry optimization at the B3LYP/6-31G* level of theory shows that in cumulenes bond length alternation (BLA) is not strictly zero and is not constant, although it is symmetrical relative to the molecule center. BLA in cumulenic cases is much smaller than in polyynic cases, so, although not strictly, the separation to cumulenes and polyynes, approximately, holds. Vibrational analysis confirms that for N even all cumulenes with coplanar methylene end groups are stable, for N odd all cumulenes with perpendicular methylene end groups are stable, and the number of hydrogen atoms at the end groups is clearly seen in all cumulenic and polyynic cases. We calculate and discuss the Density Functional Theory (DFT) ground state energy of neutral molecules, the CDFT (Constrained DFT) “ground state energy” of molecules with a hole at one end group, energy spectra, density of states, energy gap, charge and dipole moment oscillations, mean over time probabilities to find the hole at each site, coherent transfer rates, and frequency content, in general. We also compare RT-TDDFT with TB results.

APA, Harvard, Vancouver, ISO, and other styles

11

Sun, Jin, Zongling Ding, Yuanqin Yu, and Chuanmei Xie. "A Theoretical Investigation about Photoswitching of Azobenzene Adsorbed on Ag Nanoparticles." Crystals 12, no. 2 (February 11, 2022): 248. http://dx.doi.org/10.3390/cryst12020248.

Full text

Abstract:

The optical properties of hybrid systems composed of silver nanoparticles (NPs) and azobenzene molecules were systematically investigated by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the classical electrodynamics finite difference time domain (FDTD) technique for the solution of Maxwell’s equations. In order to reflect the chemical interaction between azobenzene and metal more exactly, except for adsorbed molecules, a Ag cluster separated from NP was also dealt, using RT-TDDFT. We studied the different factors affecting the surface-enhanced absorption spectra. It was found that the electric field amplified by plasmon resonance of Ag NPs can have an overall enhancement to the molecular light absorption throughout the whole energy range. The resonance between the electron and the plasmon excitation results in a larger percentage of enhancement in the absorption spectrum the closer the resonance peak is. The enhancement ratio of the resonance peak is the largest. The plasmon–exciton coupling and the optical properties of different isolate isomers influence the line shape of the absorption spectra. The dipole interaction and electronic transfer between azobenzene molecules and Ag NPs also change the shape of spectroscopy from the absorption enhancement ratio and the location of the peak. Physical and chemical factors lead to photoswitching in these hybrid systems together.

APA, Harvard, Vancouver, ISO, and other styles

12

Cho, Daeheum, Jérémy R. Rouxel, Markus Kowalewski, Prasoon Saurabh, Jin Yong Lee, and Shaul Mukamel. "Phase Cycling RT-TDDFT Simulation Protocol for Nonlinear XUV and X-ray Molecular Spectroscopy." Journal of Physical Chemistry Letters 9, no. 5 (February 16, 2018): 1072–78. http://dx.doi.org/10.1021/acs.jpclett.8b00061.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Govind, N., K. Lopata, R. Rousseau, A. Andersen, and K. Kowalski. "Visible Light Absorption of N-Doped TiO2 Rutile Using (LR/RT)-TDDFT and Active Space EOMCCSD Calculations." Journal of Physical Chemistry Letters 2, no. 21 (October 11, 2011): 2696–701. http://dx.doi.org/10.1021/jz201118r.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Chalabala, Jan, Frank Uhlig, and Petr Slavíček. "Assessment of Real-Time Time-Dependent Density Functional Theory (RT-TDDFT) in Radiation Chemistry: Ionized Water Dimer." Journal of Physical Chemistry A 122, no. 12 (March 7, 2018): 3227–37. http://dx.doi.org/10.1021/acs.jpca.8b01259.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Chen, Hanning, Jeffrey M. McMahon, Mark A. Ratner, and George C. Schatz. "Classical Electrodynamics Coupled to Quantum Mechanics for Calculation of Molecular Optical Properties: a RT-TDDFT/FDTD Approach." Journal of Physical Chemistry C 114, no. 34 (August 10, 2010): 14384–92. http://dx.doi.org/10.1021/jp1043392.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Mantela, Marilena, Andreas Morphis, Konstantinos Lambropoulos, Constantinos Simserides, and Rosa Di Felice. "Effects of Structural Dynamics on Charge Carrier Transfer in B-DNA: A Combined MD and RT-TDDFT Study." Journal of Physical Chemistry B 125, no. 16 (April 15, 2021): 3986–4003. http://dx.doi.org/10.1021/acs.jpcb.0c11489.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Lin, Yin-Pai, Dmitry Bocharov, Eugene A. Kotomin, Mikhail G. Brik, and Sergei Piskunov. "Influence of Au, Ag, and Cu Adatoms on Optical Properties of TiO2 (110) Surface: Predictions from RT-TDDFT Calculations." Crystals 12, no. 4 (March 24, 2022): 452. http://dx.doi.org/10.3390/cryst12040452.

Full text

Abstract:

In this paper, real-time time-dependent density-functional theory (RT-TDDFT) calculations are performed to analyze the optical property and charge transitions of a single noble metal atom deposited on rutile TiO2 (110) surface. The model structures are built reflecting the equilibrium positions of deposited adatoms atop the TiO2 surface. The absorption spectra are calculated for all model structures under study. To provide deeper insight into photo-absorption processes, the transition contribution maps are computed for the states of deposited adatoms involved in transitions. Assuming the photon energy is enough to overcome the band gap of TiO2 (∼3 eV), the photogenerated electrons of TiO2 seem to be partly accumulated around deposited Au atoms. In contrast, this is rarely observed for deposited Ag and Cu atoms. Based on our calculations, we have identified the transition state mechanism that is important for the design strategy of future photocatalytic materials.

APA, Harvard, Vancouver, ISO, and other styles

18

Chen, Zhanghui, and Lin-Wang Wang. "Role of initial magnetic disorder: A time-dependent ab initio study of ultrafast demagnetization mechanisms." Science Advances 5, no. 6 (June 2019): eaau8000. http://dx.doi.org/10.1126/sciadv.aau8000.

Full text

Abstract:

Despite more than 20 years of development, the underlying physics of the laser-induced demagnetization process is still debated. We present a fast, real-time time-dependent density functional theory (rt-TDDFT) algorithm together with the phenomenological atomic Landau-Lifshitz-Gilbert model to investigate this problem. Our Hamiltonian considers noncollinear magnetic moment, spin-orbit coupling (SOC), electron-electron, electron-phonon, and electron-light interactions. The algorithm for time evolution achieves hundreds of times of speedup enabling calculation of large systems. Our simulations yield a demagnetization rate similar to experiments. We found that (i) the angular momentum flow from light to the system is not essential and the spin Zeeman effect is negligible. (ii) The phonon can play a role but is not essential. (iii) The initial spin disorder and the self-consistent update of the electron-electron interaction play dominant roles and enhance the demagnetization to the experimentally observed rate. The spin disorder connects the electronic structure theory with the phenomenological three-temperature model.

APA, Harvard, Vancouver, ISO, and other styles

19

Lopata, K., R. Reslan, M. Kowalska, D. Neuhauser, N. Govind, and K. Kowalski. "Excited-State Studies of Polyacenes: A Comparative Picture Using EOMCCSD, CR-EOMCCSD(T), Range-Separated (LR/RT)-TDDFT, TD-PM3, and TD-ZINDO." Journal of Chemical Theory and Computation 7, no. 11 (October 3, 2011): 3686–93. http://dx.doi.org/10.1021/ct2005165.

Full text

APA, Harvard, Vancouver, ISO, and other styles

20

Li, Jielan, Lingyun Wan, Shizhe Jiao, Wei Hu, and Jinlong Yang. "Low-rank approximations to accelerate hybrid functional enabled real-time time-dependent density functional theory within plane waves." Electronic Structure, March 15, 2023. http://dx.doi.org/10.1088/2516-1075/acc4a0.

Full text

Abstract:

Abstract Real-time time-dependent density functional theory (RT-TDDFT) is a powerful tool for predicting excited-state dynamics. Herein, we combine the adaptively compressed exchange (ACE) operator with interpolative separable density fitting (ISDF) algorithm to accelerate the hybrid functional calculations in RT-TDDFT (hybrid RT-TDDFT) dynamics simulations for molecular and periodic systems within plane wave basis sets. Under this low-rank representation, we demonstrate that the ACE-ISDF enabled hybrid RT-TDDFT can yield accurate excited-state dynamics, but much faster than conventional calculations. Furthermore, we describe a massively parallel implementation of ACE-ISDF enabled hybrid RT-TDDFT dynamics simulations containing thousands of atoms (1,728 atoms), which can scale up to 3,456 CPU cores on modern heterogeneous supercomputers.

APA, Harvard, Vancouver, ISO, and other styles

21

Han, Ruocheng, Johann Mattiat, and Sandra Luber. "Automatic purpose-driven basis set truncation for time-dependent Hartree–Fock and density-functional theory." Nature Communications 14, no. 1 (January 6, 2023). http://dx.doi.org/10.1038/s41467-022-35694-4.

Full text

Abstract:

AbstractReal-time time-dependent density-functional theory (RT-TDDFT) and linear response time-dependent density-functional theory (LR-TDDFT) are two important approaches to simulate electronic spectra. However, the basis sets used in such calculations are usually the ones designed mainly for electronic ground state calculations. In this work, we propose a systematic and robust scheme to truncate the atomic orbital (AO) basis set employed in TDDFT and TD Hartree–Fock (TDHF) calculations. The truncated bases are tested for both LR- and RT-TDDFT as well as RT-TDHF approaches, and provide an acceleration up to an order of magnitude while the shifts of excitation energies of interest are generally within 0.2 eV. The procedure only requires one extra RT calculation with 1% of the total propagation time and a simple modification on basis set file, which allows an instant application in any quantum chemistry package supporting RT-/LR-TDDFT calculations. Aside from the reduced computational effort, this approach also offers valuable insight into the effect of different basis functions on computed electronic excitations and further ideas on the design of basis sets for special purposes.

APA, Harvard, Vancouver, ISO, and other styles

22

Huang, Xunkun, Wenshu Zhang, and WanZhen Liang. "Time-dependent Kohn−Sham electron dynamics coupled with nonequilibrium plasmonic response via atomistic electromagnetic model." Journal of Chemical Physics 160, no. 21 (June 3, 2024). http://dx.doi.org/10.1063/5.0205845.

Full text

Abstract:

Computational modeling of plasmon-mediated molecular photophysical and photochemical behaviors can help us better understand and tune the bound molecular properties and reactivity and make better decisions to design and control nanostructures. However, computational investigations of coupled plasmon–molecule systems are challenging due to the lack of accurate and efficient protocols to simulate these systems. Here, we present a hybrid scheme by combining the real-time time-dependent density functional theory (RT-TDDFT) approach with the time-domain frequency dependent fluctuating charge (TD-ωFQ) model. At first, we transform ωFQ in the frequency-domain, an atomistic electromagnetic model for the plasmonic response of plasmonic metal nanoparticles (PMNPs), into the time-domain and derive its equation-of-motion formulation. The TD-ωFQ introduces the nonequilibrium plasmonic response of PMNPs and atomistic interactions to the electronic excitation of the quantum mechanical (QM) region. Then, we combine TD-ωFQ with RT-TDDFT. The derived RT-TDDFT/TD-ωFQ scheme allows us to effectively simulate the plasmon-mediated “real-time” electronic dynamics and even the coupled electron–nuclear dynamics by combining them with the nuclear dynamics approaches. As a first application of the RT-TDDFT/TD-ωFQ method, we study the nonradiative decay rate and plasmon-enhanced absorption spectra of two small molecules in the proximity of sodium MNPs. Thanks to the atomistic nature of the ωFQ model, the edge effect of MNP on absorption enhancement has also been investigated and unveiled.

APA, Harvard, Vancouver, ISO, and other styles

23

Ranka, Karnamohit, and Christine M. Isborn. "Size-dependent errors in real-time electron density propagation." Journal of Chemical Physics 158, no. 17 (May 1, 2023). http://dx.doi.org/10.1063/5.0142515.

Full text

Abstract:

Real-time (RT) electron density propagation with time-dependent density functional theory (TDDFT) or Hartree–Fock (TDHF) is one of the most popular methods to model the charge transfer in molecules and materials. However, both RT-TDHF and RT-TDDFT within the adiabatic approximation are known to produce inaccurate evolution of the electron density away from the ground state in model systems, leading to large errors in charge transfer and erroneous shifting of peaks in absorption spectra. Given the poor performance of these methods with small model systems and the widespread use of the methods with larger molecular and material systems, here we bridge the gap in our understanding of these methods and examine the size-dependence of errors in RT density propagation. We analyze the performance of RT density propagation for systems of increasing size during the application of a continuous resonant field to induce Rabi-like oscillations, during charge-transfer dynamics, and for peak shifting in simulated absorption spectra. We find that the errors in the electron dynamics are indeed size dependent for these phenomena, with the largest system producing the results most aligned with those expected from linear response theory. The results suggest that although the RT-TDHF and RT-TDDFT methods may produce severe errors for model systems, the errors in charge transfer and resonantly driven electron dynamics may be much less significant for more realistic, large-scale molecules and materials.

APA, Harvard, Vancouver, ISO, and other styles

24

Michos, F. I., A. G. Chronis, C. S. Garoufalis, and M. M. Sigalas. "Optical properties of Cu, Ag and Au nanoparticles with different sizes and shapes." Applied Research, January 24, 2024. http://dx.doi.org/10.1002/appl.202300101.

Full text

Abstract:

AbstractThe absorption spectra of various sizes of nanoparticles of copper (Cu), silver (Ag), and gold (Au) are theoretically investigated. The Density Functional Theory (DFT), Time Dependent DFT (TDDFT), and Real Time TDDFT (RT‐TDDFT) are used to demonstrate how size and shape affect their optical properties and how these are evolved as the number of atoms increases. For this reason, the focus was turned on almost spherical NPs cut out from the corresponding crystal structure (called 0D), elongated ones (1D) and flattened ones (2D). The nature of the observed absorption peaks is further analyzed with the help of transition contribution maps (TCM) and induced density plots which help us identify the emergence of probable plasmonic resonances as the size of the nanoparticles increases.This article is protected by copyright. All rights reserved.

APA, Harvard, Vancouver, ISO, and other styles

25

Ye, Linfeng, Hao Wang, Yong Zhang, and Wenjian Liu. "Self-Adaptive Real-Time Time-Dependent Density Functional Theory for X-ray Absorptions." Journal of Chemical Physics, July 29, 2022. http://dx.doi.org/10.1063/5.0106250.

Full text

Abstract:

Real-time time-dependent density functional theory (RT-TDDFT) can in principle access the whole absorption spectrum of a many-electron system exposed to a narrow pulse. However, this requires an accurate and efficient propagator for the numerical integration of the time-dependent Kohn-Sham equation. While a low-order time propagator is already sufficient for the low-lying valence absorption spectra, it is no longer the case for the X-ray absorption spectra (XAS) of systems composed even only of light elements, for which the use of a high-order propagator is indispensable. It is then crucial to choose a largest possible time step and a shortest possible simulation time, so as to minimize the computational cost. To this end, we propose here a robust AutoPST approach to determine automatically (Auto) the propagator (P), step (S), and time (T) for relativistic RT-TDDFT simulations of XAS.

APA, Harvard, Vancouver, ISO, and other styles

26

Ramakrishna, Kushal, Mani Lokamani, Andrew Baczewski, Jan Vorberger, and Attila Cangi. "Impact of Electronic Correlations on High-Pressure Iron: Insights from Time-Dependent Density Functional Theory." Electronic Structure, September 26, 2023. http://dx.doi.org/10.1088/2516-1075/acfd75.

Full text

Abstract:

Abstract We present a comprehensive investigation of the electrical and thermal conductivity of iron under high pressures at ambient temperature, employing the real-time formulation of time-dependent density functional theory (RT-TDDFT). Specifically, we examine the influence of a Hubbard correction (+U) to account for strong electron correlations. Our calculations based on RT-TDDFT demonstrate that the evaluated electrical conductivity for both high-pressure body-centered cubic (BCC) and hexagonal close-packed (HCP) iron phases agrees well with experimental data. Furthermore, we explore the anisotropy in the thermal conductivity of HCP iron under high pressure, and our findings are consistent with experimental observations. Interestingly, we find that the incorporation of the +U correction significantly impacts the ground state and linear response properties of iron at pressures below 50 GPa, with its influence diminishing as pressure increases. This study offers valuable insights into the influence of electronic correlations on the electronic transport properties of iron under extreme conditions.

APA, Harvard, Vancouver, ISO, and other styles

27

Nadler, Roger, and Javier Fdez Sanz. "Simulating the optical properties of CdSe clusters using the RT-TDDFT approach." Theoretical Chemistry Accounts 132, no. 4 (February 9, 2013). http://dx.doi.org/10.1007/s00214-013-1342-z.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

De Santis, Matteo, Valérie Vallet, and André Severo Pereira Gomes. "Environment Effects on X-Ray Absorption Spectra With Quantum Embedded Real-Time Time-Dependent Density Functional Theory Approaches." Frontiers in Chemistry 10 (February 28, 2022). http://dx.doi.org/10.3389/fchem.2022.823246.

Full text

Abstract:

In this work we implement the real-time time-dependent block-orthogonalized Manby-Miller embedding (rt-BOMME) approach alongside our previously developed real-time frozen density embedding time-dependent density functional theory (rt-TDDFT-in-DFT FDE) code, and investigate these methods’ performance in reproducing X-ray absorption spectra (XAS) obtained with standard rt-TDDFT simulations, for model systems comprised of solvated fluoride and chloride ions ([X@(H2O)8−, X = F, Cl). We observe that for ground-state quantities such as core orbital energies, the BOMME approach shows significantly better agreement with supermolecular results than FDE for the strongly interacting fluoride system, while for chloride the two embedding approaches show more similar results. For the excited states, we see that while FDE (constrained not to have the environment densities relaxed in the ground state) is in good agreement with the reference calculations for the region around the K and L1 edges, and is capable of reproducing the splitting of the 1s1 (n + 1)p1 final states (n + 1 being the lowest virtual p orbital of the halides), it by and large fails to properly reproduce the 1s1 (n + 2)p1 states and misses the electronic states arising from excitation to orbitals with important contributions from the solvent. The BOMME results, on the other hand, provide a faithful qualitative representation of the spectra in all energy regions considered, though its intrinsic approximation of employing a lower-accuracy exchange-correlation functional for the environment induces non-negligible shifts in peak positions for the excitations from the halide to the environment. Our results thus confirm that QM/QM embedding approaches are viable alternatives to standard real-time simulations of X-ray absorption spectra of species in complex or confined environments.

APA, Harvard, Vancouver, ISO, and other styles

29

Liu, Wen-Hao, Jun-Wei Luo, Shu-Shen Li, and Lin-Wang Wang. "The critical role of hot carrier cooling in optically excited structural transitions." npj Computational Materials 7, no. 1 (July 22, 2021). http://dx.doi.org/10.1038/s41524-021-00582-w.

Full text

Abstract:

AbstractThe hot carrier cooling occurs in most photoexcitation-induced phase transitions (PIPTs), but its role has often been neglected in many theoretical simulations as well as in proposed mechanisms. Here, by including the previously ignored hot carrier cooling in real-time time-dependent density functional theory (rt-TDDFT) simulations, we investigated the role of hot carrier cooling in PIPTs. Taking IrTe2 as an example, we reveal that the cooling of hot electrons from the higher energy levels of spatially extended states to the lower energy levels of the localized Ir–Ir dimer antibonding states strengthens remarkably the atomic driving forces and enhances atomic kinetic energy. These two factors combine to dissolute the Ir–Ir dimers on a timescale near the limit of atomic motions, thus initiating a deterministic kinetic phase transition. We further demonstrate that the subsequent cooling induces nonradiative recombination of photoexcited electrons and holes, leading to the ultrafast recovery of the Ir–Ir dimers observed experimentally. These findings provide a complete picture of the atomic dynamics in optically excited structural phase transitions.

APA, Harvard, Vancouver, ISO, and other styles

30

Li, Yi, Dong-Dong Kang, Jia-Yu Dai, and Lin-Wang Wang. "The cage effect of electron beam irradiation damage in cryo-electron microscopy." npj Computational Materials 10, no. 1 (May 30, 2024). http://dx.doi.org/10.1038/s41524-024-01299-2.

Full text

Abstract:

AbstractElectron beam irradiation can cause damage to biological and organic samples, as determined via transmission electron microscopy (TEM). Cryo-electron microscopy (cryo-EM) significantly reduces such damage by quickly freezing the environmental water around organic molecules. However, there are multiple hypotheses about the mechanism of cryo-protection in cryo-EM. A lower temperature can cause less molecular dissociation in the first stage, or frozen water can have a “cage” effect by preventing the dissociated fragments from flying away. In this work, we use real-time time-dependent density functional theory molecular dynamics(rt-TDDFT-MD) simulations to study the related dynamics. We use our recently developed natural orbital branching (NOB) algorithm to describe the molecular dissociation process after the molecule is ionized. We find that despite the difference in surrounding water molecules at different temperatures, the initial dissociation process is similar. On the other hand, the dissociated fragments fly away at room temperature, while they remain in the same cage when frozen water is used. Our results provide direct support for the cage effect mechanism.

APA, Harvard, Vancouver, ISO, and other styles

31

Gao, Nan, Guodong Zhu, Yingzhou Huang, and Yurui Fang. "Plasmonic Hybridization Properties in Polyenes Octatetraene Molecules based on Theoretical Computation." Chinese Physics B, August 12, 2022. http://dx.doi.org/10.1088/1674-1056/ac891c.

Full text

Abstract:

Abstract Due to the continuous emergence of molecular and cluster devices or systems, the relationship between the plasmonic properties of multiple clusters and the molecular interactions and properties of a single cluster or molecule has become increasingly important. A hybrid phenomenon similar to plasmonic nanoparticle hybridization exists between two molecules with plasmon excitation modes. We use linear-response time-dependent density functional theory (LRTDDFT), real-time propagation time-dependent density functional theory (RT-TDDFT), the plasmonicity index (PI) and transition contribution maps (TCMs) to identify the plasmon excitation modes for the linear polyenes octatetraene with -OH and -NH 2 groups and analyze the hybridization characteristics using charge transitions. The results show that molecular plasmon hybridization exists when the two molecules are coupled. The TCM analysis shows that the plasmon modes and hybridization are the results of collective and single-particle excitation. The plasmon mode is stronger, and the individual properties of the molecules are maintained after coupling when there is extra charge depose in the molecules because the electrons are moving in the molecules. This study provides new insights into the molecular plasmon hybridization of coupled molecules.

APA, Harvard, Vancouver, ISO, and other styles

32

Deng, Zun-Yi, Zhihua Hu, and Hong-Jian Feng. "Dynamic interplay between thionine and DNA under carbon ion irradiation:a real-time first-principles study." Journal of Physics: Condensed Matter, November 3, 2022. http://dx.doi.org/10.1088/1361-648x/ac9fff.

Full text

Abstract:

Abstract Understanding the interactions between DNA and photosensitizer under ion irradiation benefits the development of aptasensors, DNA biosensors and cancer diagnosis. Using real-time time-depended density functional theory (rt-TDDFT), by simulating high-energy C ion passing through DNA with poly(dG)·poly(dC) sequence and that with embedded thionine (3,7-diamino-5-phenothiazinium, TH), we compared the electronic stopping power (ESP), evolution of the structure and charge, and absorption spectrum. TH inserting leads the increase in space charge density, a larger electron deexcitation and a larger ESP, but the speed corresponding to the maximum ESP is almost same. When C ion passes through TH-DNA, the structure of TH slightly changes and there still exists noncovalent interaction between TH and DNA, but the absorption coefficient depends on the electron occupied state of TH when the ion passes through. These results indicate that at low radiation doses, TH still can be a DNA detector, although its response wavelength and intensity have been slightly changed, and provide a theoretical reference to improve the possible application of phenothiazine dye in DNA biosensor under ion irradiation.

APA, Harvard, Vancouver, ISO, and other styles

33

Lin, Peize, Xinguo Ren, Xiaohui Liu, and Lixin He. "Ab initio electronic structure calculations based on numerical atomic orbitals: Basic fomalisms and recent progresses." WIREs Computational Molecular Science, September 12, 2023. http://dx.doi.org/10.1002/wcms.1687.

Full text

Abstract:

AbstractThe numerical atomic orbital (NAO) basis sets offer a computationally efficient option for electronic structure calculations, as they require fewer basis functions compared with other types of basis sets. Moreover, their strict localization allows for easy combination with current linear scaling methods, enabling efficient calculation of large physical systems. In recent years, NAO bases have become increasingly popular in modern electronic structure codes. This article provides a review of the ab initio electronic structure calculations using NAO bases. We begin by introducing basic formalisms of the NAO‐based electronic structure method, including NAO base set generation, self‐consistent calculations, force, and stress calculations. We will then discuss some recent advances in the methods based on the NAO bases, such as real‐time dependent density functional theory (rt‐TDDFT), efficient implementation of hybrid functionals, and other advanced electronic structure methods. Finally, we introduce the ab initio tight‐binding model, which can be generated directly after the self‐consistent calculations. The model allows for efficient calculation of electronic structures, and the associated topological, and optical properties of the systems.This article is categorized under: Electronic Structure Theory > Ab Initio Electronic Structure Methods Electronic Structure Theory > Density Functional Theory Structure and Mechanism > Computational Materials Science

APA, Harvard, Vancouver, ISO, and other styles

34

Shomali, Elaheh, Markus E. Gruner, and Rossitza Pentcheva. "Concerted Mechanism of Carrier Dynamics in Laser‐Excited Fe_n/(MgO)_m(001) Heterostructures from Real‐Time Time‐Dependent DFT." Advanced Theory and Simulations, October 25, 2023. http://dx.doi.org/10.1002/adts.202300319.

Full text

Abstract:

AbstractUsing real‐time time‐dependent density functional theory (RT‐TDDFT), the electronic response of a Fen/(MgO)m(001) (n=1,3,5 and m=3,5,7) metal/insulator heterostructure to an optical excitation is calculated, considering laser frequencies below, near, and above the bandgap of the insulator and two directions of polarization. The spatial redistribution of electronic charge after illumination shows a strong dependence on the frequency and polarization direction of the laser pulse with a similar pattern for all thicknesses. The comparison of the layer‐resolved changes in occupation of the ground‐state orbitals after optical excitation obtained for Fen/(MgO)m(001) and bulk Fe reveals the origin of excited carriers in the heterostructures: In the central and interface Fe layers carriers are excited from states in the vicinity of the Fermi‐level to the conduction band of MgO. Simultaneously, excitations take place from the valence band of MgO to Fe states above the Fermi‐level. This concerted mechanism allows for an effective bidirectional relocation of excited carriers between the metallic and insulating subsystems in heterostructures with a thickness of several nanometers, providing an effective accumulation of hot carriers in the insulating layers, even at photon energies in the vicinity and below the bandgap of bulk MgO.

APA, Harvard, Vancouver, ISO, and other styles

35

Deng, Zun-Yi, and Hong-Jian Feng. "Real-time first-principles calculations of ultrafast carrier dynamics of SnSe/TiO2 heterojunction under Li+ implantation." Journal of Physics: Condensed Matter, June 16, 2022. http://dx.doi.org/10.1088/1361-648x/ac7997.

Full text

Abstract:

Abstract Ion implantation has been widely used in biomaterials, alloys, and semiconductors modification. Basing on the studying of trapping states in the equilibrium state, we investigate the ultrafast carrier dynamics of SnSe/TiO2 and SnSe/Li/TiO2 heterojunctions under Li+ implantation by the real-time time-dependent density functional theory (RT-TDDFT). The special type II band alignment and Li+ interfacial states in SnSe/TiO2 heterojunction effectively facilitate the exciton dissociation in a benign process and suppresses the interfacial nonradiative recombination. By monitoring the instantaneous ion-solid interaction energy, electronic stropping power and the excitation electron evolution, we find that atomic reconstruction introduced by the Li inserting layer changes the charge density and crystal potential field in the injection channel, and thus weakens the violent oscillation force and electron excitation on the Ti and O atoms. There exists a weaker and shorter charge excitation at the interface for SnSe/Li/TiO2 implantation system, which suggests that the Li ion layer weakens the e-ph coupling between the interface electrons and the moving ion. Meanwhile, only the hot electrons are produced in the interface region, reducing the probability of carrier recombination. These results provide an understanding for the behavior of carriers in SnSe based heterojunctions and the electron-phonon coupling mechanism at the phase/grain boundary under ion implantation.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'RT-TDDFT'

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