Accurate nonadiabatic quantum dynamics on the cheap: Making the most of mean field theory with master equations

Kelly, Aaron; Brackbill, Nora; Markland, Thomas E.

doi:10.1063/1.4913686

Cited by 63 publications

(80 citation statements)

References 52 publications

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“…Even though the Ehrenfest method performs poorly for these systems, its accuracy can be improved by combining it with the generalized quantum master equation. 60 In this way, observables are calculated via a memory kernel that generally decays much faster than the observables themselves, so that one can make the most out of the short-time dynamics. It would be interesting to try the same trick for our method, to compute long-time dynamics from short simulations and (potentially) further improve the accuracy.…”

Section: Resultsmentioning

confidence: 99%

Spin-mapping approach for nonadiabatic molecular dynamics

Runeson

Richardson

2019

The Journal of Chemical Physics

165

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We propose a trajectory-based method for simulating nonadiabatic dynamics in molecular systems with two coupled electronic states. Employing a quantum-mechanically exact mapping of the two-level problem to a spin-1 2 coherent state, we construct a classical phase space of a spin vector constrained to a spherical surface with a radius consistent with the quantum magnitude of the spin. In contrast with the singly-excited harmonic oscillator basis used in Meyer-Miller-Stock-Thoss (MMST) mapping, the theory requires no additional projection operators onto the space of physical states. When treated under a quasiclassical approximation, we show that the resulting dynamics is equivalent to that generated by the MMST Hamiltonian. What differs is the value of the zero-point energy parameter as well as the initial distribution and the measurement operators. For various spin-boson models the results of our method are seen to be a significant improvement compared to both standard Ehrenfest dynamics and linearized semiclassical MMST mapping, without adding any computational complexity.

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Section: Resultsmentioning

confidence: 99%

Spin-mapping approach for nonadiabatic molecular dynamics

Runeson

Richardson

2019

The Journal of Chemical Physics

165

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“…51 Here, the damping constant γ determines the width and peak position of the spectral density (Λ is the reorganization energy as defined in section 2.2). It should be noted that while only a few local phonon modes are selected when employing Ehrenfest dynamics to describe CS dynamics, continuous spectrum of phonon modes, J(ω), is employed when 59 proposed a method that combines Ehrenfest mean field theory with the reduced density matrix formalism, which is a non-perturbative, non-Markovian, and non-restrictive on the form of the Hamiltonian with a much lower computational cost than mean-field theory. In this work we choose two different approaches, Ehrenfest dynamics in short times and Redfield theory in long times, which are known to be well-suited in each regime.…”

Section: 50mentioning

confidence: 99%

Charge Dynamics in Organic Photovoltaic Materials: Interplay between Quantum Diffusion and Quantum Relaxation

2015

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Original citation:Lee, Myeong H., Aragó, Juan and Troisi, Alessandro. (2015) Charge dynamics in organic photovoltaic materials : interplay between quantum diffusion and quantum relaxation. The Journal of Physical Chemistry Part C, 119 (27). pp. 14989-14998. Permanent WRAP url:http://wrap.warwick.ac.uk/73402 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry Part C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work, see http://dx.doi.org/10.1021/acs.jpcc.5b03989 A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. For more information, please contact the WRAP This paper discusses the mechanism of generation of free charges in organic photovoltaic cells (OPV) from electrostatically bound electron-hole pairs. The efficiency of this process is explained when interfacial charge-transfer (CT) states are generated by direct optical excitation. We used semiclassical quantum dynamics at short timescale (∼100 fs) and Redfield theory at relatively long timescale (∼10-100 ps) to cover both the process of dissociation and the relaxation to the lowest energy state. Our calculations suggest that a CT state with an intermediate electron-hole separation can evolve into a charge-separated (CS) state on ultrafast timescales (∼100 fs) as a result of quantum diffusion. On long timescales, however, the CS states ultimately relax to the low-energy CT states due to the interaction with the thermal bath, indicating that the yield of free charge carrier generation is determined by the interplay between ultrafast charge separation, due to quantum diffusion, and the much slower quantum relaxation process.

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“…In this work, we investigate the mechanism of exciton dissociation and charge separation in model OPV interfaces using a nonadiabatic dynamics simulation technique called the forward-backward trajectory solution (FBTS) of the quantum-classical Liouville equation 54 . The FBTS algorithm can be rigorously derived from exact quantum dynamics 55 , is systematically improvable 56 , and is typically more accurate than Ehrenfest mean field theory and perturbative methods [56][57][58] , while retaining a reasonable computational cost. We report benchmark comparisons of FBTS simulation results with recently available, highly accurate, hierarchical equationsof-motion (HEOM) data 34,50 , for a number of different parameter regimes in low-dimensional lattice models for the donor-acceptor interface.…”

Section: Introductionmentioning

confidence: 99%

Exciton dissociation and charge separation at donor–acceptor interfaces from quantum-classical dynamics simulations

Kelly

2020

Faraday Discuss.

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In organic photovoltaic (OPV) systems, exciton dissociation and ultrafast charge separation at donor-acceptor heterojunctions both play a key role in controlling the efficiency of the conversion of excitation energy into free charge carriers. In this work, nonadiabatic dynamics simulations based on the quantum-classical Liouville equation, are employed to study the real-time dynamics of exciton dissociation and charge separation at a model donor-acceptor interface. Benchmark comparisons for a variety of low dimensional donor-acceptor chain models are performed to assess the accuracy of the quantum classical dynamics technique referred to as the forward-backward trajectory solution (FBTS). Although not always quantitative, the FBTS approach offers a reasonable balance between accuracy and computational cost. The short-time dynamics of exciton dissociation in related higher-dimensional lattice models for the interface are also investigated to assess the effect of the dimensionality on the first steps in the mechanism of charge carrier generation.

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Accurate nonadiabatic quantum dynamics on the cheap: Making the most of mean field theory with master equations

Cited by 63 publications

References 52 publications

Spin-mapping approach for nonadiabatic molecular dynamics

Spin-mapping approach for nonadiabatic molecular dynamics

Charge Dynamics in Organic Photovoltaic Materials: Interplay between Quantum Diffusion and Quantum Relaxation

Exciton dissociation and charge separation at donor–acceptor interfaces from quantum-classical dynamics simulations

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