Machine-Learned Kohn–Sham Hamiltonian Mapping for Nonadiabatic Molecular Dynamics

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(8), P. 2992 - 3007

Published: April 6, 2024

In this work, we report a simple, efficient, and scalable machine-learning (ML) approach for mapping non-self-consistent Kohn-Sham Hamiltonians constructed with one kind of density functional to the nearly self-consistent another functional. This is designed as fast surrogate Hamiltonian calculator use in long nonadiabatic dynamics simulations large atomistic systems. approach, input output features are matrices computed from different levels theory. We demonstrate that developed ML-based method (1) speeds up calculations by several orders magnitude, (2) conceptually simpler than alternative ML approaches, (3) applicable systems sizes can be used arbitrary functionals, (4) requires modest training data, learns fast, generates molecular orbitals their energies accuracy matching conventional calculations, (5) when applied simulation excitation energy relaxation yields corresponding time scales within margin error calculations. Using explore C

Language: Английский

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Significant Impact of Defect Fluctuation on Charge Dynamics in CsPbI₃: A Study Combining Machine Learning with Quantum Dynamics

The Journal of Physical Chemistry Letters, Journal Year: 2024, Volume and Issue: 15(14), P. 3764 - 3771

Published: March 29, 2024

In this study, we developed a machine-learned force field for CsPbI3 using neural network potential, enabling molecular dynamics simulations (MD) with ab initio accuracy over nanoseconds. This approach, combined MD and nonadiabatic MD, was used to study the charge trapping recombination in both pristine defective CsPbI3. Our revealed key transitions affecting carrier lifetimes, especially systems iodine vacancy interstitial defects. An trimer, formed when replaces cesium, exhibits high-frequency phonon mode. mode enhances coupling, accelerating compared ones. system, times varied significantly due differences NA coupling energy gaps. The interplay between pure dephasing time is crucial determining findings highlight role of defect evolution perovskites, offering insights enhancing perovskite performance.

Language: Английский

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Nuclear Quantum Effects Accelerate Hot Carrier Relaxation but Slow Down Recombination in Metal Halide Perovskites

Journal of the American Chemical Society, Journal Year: 2025, Volume and Issue: unknown

Published: March 19, 2025

Inorganic semiconductors are composed of heavy elements whose vibrational motions well described by classical mechanics. Heavy elements, such as Pb and I, support charge carriers in metal halide perovskites. Nevertheless, the soft structure strong coupling between organic inorganic components create conditions which nuclear quantum effects (NQEs) can play important roles. By combining ab initio, ring-polymer, nonadiabatic molecular dynamics approaches with time-domain density functional theory, we demonstrate how NQEs influence structural electronic properties electron-vibrational hybrid organic-inorganic (MAPbI3) all-inorganic (CsPbI3) Quantum zero-point fluctuations enhance disorder, reduce band gap, accelerate elastic scattering responsible for coherence loss. have opposite influences on intraband carrier relaxation interband recombination. These inelastic events governed product overlap-like electron-phonon matrix element atomic velocity. overlap increases The involves many states. Reduction some states is offset other pathways, while an increased velocity makes faster. Electron-hole band-edge plays a key role recombination, its reduction NQEs-enhanced disorder recombination slower. This phenomenon seen both MAPbI3 CsPbI3 much more pronounced when light component present. study offers detailed understanding processes perovskites, offering theoretical insights into hot that govern performance solar cells optoelectronic devices.

Language: Английский

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Ag–Bi Charge Redistribution Creates Deep Traps in Defective Cs₂AgBiBr₆: Machine Learning Analysis of Density Functional Theory

The Journal of Physical Chemistry Letters, Journal Year: 2022, Volume and Issue: 13(16), P. 3645 - 3651

Published: April 18, 2022

Lead-free double perovskites hold promise for stable and environmentally benign solar cells; however, they exhibit low efficiencies because defects act as charge recombination centers. Identifying trap-assisted loss mechanisms developing defect passivation strategies constitute an urgent goal. Applying unsupervised machine learning to density functional theory nonadiabatic molecular dynamics, we demonstrate that negatively charged Br vacancies in Cs2AgBiBr6 create deep hole traps through redistribution between the adjacent Ag Bi atoms. Vacancy electrons are first accepted by then shared with Ag, trap transforms from shallow deep. Subsequent losses promoted motions perpendicular rather than along Ag-Bi axis, can be expected. In contrast, pristine correlates most displacements of Cs atoms Br-Br-Br angles. Doping replace at vacancy maintains keeps shallow.

Language: Английский

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Electron-Volt Fluctuation of Defect Levels in Metal Halide Perovskites on a 100 ps Time Scale

The Journal of Physical Chemistry Letters, Journal Year: 2022, Volume and Issue: 13(25), P. 5946 - 5952

Published: June 22, 2022

Metal halide perovskites (MHPs) have gained considerable attention due to their excellent optoelectronic performance, which is often attributed unusual defect properties. We demonstrate that midgap levels can exhibit very large and slow energy fluctuations associated with anharmonic acoustic motions. Therefore, care should be taken classifying MHP defects as deep or shallow, since shallow may become vice versa. As a consequence, charges from escape into bands, light absorption extended longer wavelengths, improving material performance. The phenomenon, demonstrated iodine vacancy in CH3NH3PbI3 using machine learning force field, expected for variety of dopants many MHPs other soft inorganic semiconductors. Since large-scale motions precursors chemical decomposition, known problem MHPs, we propose materials are stiffer than but softer traditional semiconductors, such Si TiO2, simultaneously performance stability.

Language: Английский

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Fluctuations at Metal Halide Perovskite Grain Boundaries Create Transient Trap States: Machine Learning Assisted Ab Initio Analysis

ACS Applied Materials & Interfaces, Journal Year: 2022, Volume and Issue: 14(50), P. 55753 - 55761

Published: Dec. 7, 2022

All-inorganic perovskites are promising candidates for solar energy and optoelectronic applications, despite their polycrystalline nature with a large density of grain boundaries (GBs) due to facile solution-processed fabrication. GBs exhibit complex atomistic structures undergoing slow rearrangements. By studying evolution the Σ5(210) CsPbBr3 GB on nanosecond time scale, comparable charge carrier lifetimes, we demonstrate that deformations appear every ∼100 ps increase significantly probability deep traps. However, traps form only transiently few hundred femtoseconds. In contrast, shallow continuously at GB. Shallow localized in layer, while sublayer, which is still distorted from pristine structure can be jammed unfavorable conformations. The electronic properties correlate bond angles, notable exception Br-Br distance, provides signature halide migration along GBs. transient trap states localization electrons holes different parts indicate lifetimes should long. At same time, mobility reduced. complex, multiscale geometric rationalize contradictory statements made literature regarding both benign detrimental roles perovskite performance provide new insights into properties.

Language: Английский

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Ultrafast and Nanoscale Energy Transduction Mechanisms and Coupled Thermal Transport across Interfaces

ACS Nano, Journal Year: 2023, Volume and Issue: 17(15), P. 14253 - 14282

Published: July 17, 2023

The coupled interactions among the fundamental carriers of charge, heat, and electromagnetic fields at interfaces boundaries give rise to energetic processes that enable a wide array technologies. energy transduction these results in thermal dissipation surfaces, often quantified by boundary resistance, thus driving functionalities modern nanotechnologies are continuing provide transformational benefits computing, communication, health care, clean energy, power recycling, sensing, manufacturing, name few. It is purpose this Review summarize recent works have been reported on ultrafast nanoscale heat transfer mechanisms across when different couple near or interfaces. We review solids, liquids, gasses, plasmas drive resulting interfacial temperature gradients due momentum coupling various combinations electrons, vibrons, photons, polaritons (plasmon phonon polaritons), molecules. These transport with involve relatively research, thus, several opportunities exist further develop nascent fields, which we comment throughout course Review.

Language: Английский

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Zeno and Anti-Zeno Effects in Nonadiabatic Molecular Dynamics

The Journal of Physical Chemistry Letters, Journal Year: 2023, Volume and Issue: 14(32), P. 7274 - 7282

Published: Aug. 9, 2023

Decoherence plays an important role in nonadiabatic (NA) molecular dynamics (MD) simulations because it provides a physical mechanism for trajectory hopping and can alter transition rates by orders of magnitude. Generally, decoherence effects slow quantum transitions, as exemplified the Zeno effect: limit infinitely fast decoherence, transitions stop. If measurements are not sufficiently frequent, opposite anti-Zeno effect occurs, which accelerated with faster decoherence. Using two common NA-MD approaches, fewest switches surface decoherence-induced hopping, combined analytic examination, we demonstrate that including into slows down NA transitions; however, many realistic systems operate regime. Therefore, is methods describe both effects. Numerical charge trapping relaxation graphitic carbon nitride suggest time-dependent Hamiltonians encountered produce robust results respect to errors time, favorable feature simulations.

Language: Английский

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Generalized nonequilibrium Fermi’s golden rule and its semiclassical approximations for electronic transitions between multiple states

The Journal of Chemical Physics, Journal Year: 2024, Volume and Issue: 160(3)

Published: Jan. 19, 2024

The nonequilibrium Fermi's golden rule (NE-FGR) approach is developed to simulate the electronic transitions between multiple excited states in complex condensed-phase systems described by recently proposed multi-state harmonic (MSH) model Hamiltonian. MSH models were constructed faithfully capture photoinduced charge transfer dynamics a prototypical organic photovoltaic carotenoid-porphyrin-C60 molecular triad dissolved tetrahydrofuran. A general expression of fully quantum-mechanical NE-FGR rate coefficients for all pairs obtained. Besides, linearized semiclassical formula and series approximations featuring Wigner classical nuclear sampling choices different during quantum coherence period are derived. current enables possible population pathways triad, contrast previous applications that only addressed donor-to-acceptor transition. Our simulations two conformations serve as demonstration benchmarking show difference levels approximation small system, especially at room temperature. By comparing with nonadiabatic dynamics, we observe similar timescales predicted NE-FGR. It believed formulation Hamiltonian variety realistic systems.

Language: Английский

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Decoherence ensures convergence of non-adiabatic molecular dynamics with number of states

The Journal of Chemical Physics, Journal Year: 2024, Volume and Issue: 161(6)

Published: Aug. 9, 2024

Non-adiabatic (NA) molecular dynamics (MD) is a powerful approach for studying far-from-equilibrium quantum in photophysical and photochemical systems. Most NA-MD methods are developed tested with few-state models, their validity complex systems involving many states not well studied. By modeling intraband equilibration interband recombination of charge carriers MoS2, we investigate the convergence three popular algorithms, fewest switches surface hopping (FSSH), global flux (GFSH), decoherence induced (DISH) number states. Only standard DISH algorithm converges produces Boltzmann equilibrium. Unitary propagation wave function FSSH GFSH violates distribution, leads to internal inconsistency between time-dependent Schrödinger equation state populations trajectory counts, non-convergent results. Introducing by collapsing fixes these problems. The simplified version that omits projecting out occupied applicable also causes problems when increased. We discuss algorithmic application collapse detailed balance provide FSSH, GFSH, flow charts. use convergent highly important complicated processes multiple Our findings basis investigating realistic

Language: Английский

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