A modified Ehrenfest method that achieves Boltzmann quantum state populations

Bastida, Adolfo; Cruz, Carlos; Zúñiga, José; Requena, A.; Miguel, Beatriz

doi:10.1016/j.cplett.2005.10.008

Cited by 51 publications

(75 citation statements)

References 27 publications

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“…A major drawback of Ehrenfest dynamics is that it fails to achieve thermal equilibrium, 39,40 e.g., non-Boltzmann distribution of equilibrium state population, and does not properly account for decoherence. [41][42][43] Several approaches are being debated in the literature to improve long-time behavior [44][45][46] and incorporate decoherence effects 41,47 in Ehrenfest dynamics, but they are outside the scope of our analysis.…”

Section: Reduced Density Matrix Dynamicsmentioning

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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Section: Reduced Density Matrix Dynamicsmentioning

confidence: 99%

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

2015

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“…29,40,45,47 In addition to comparing the results of density matrix calculation with those of mean-field Ehrenfest dynamics, the results from a temperature-corrected Ehrenfest dynamics variant are also investigated. This scheme, by Bastida et al, [48][49][50][51] introduced an additional correction factor to fulfill detailed balance and leads to the correct thermal distribution at long times. An improved version of this algorithm will be proposed and tested.…”

Section: Introductionmentioning

confidence: 99%

Juxtaposing density matrix and classical path-based wave packet dynamics

Aghtar

Liebers

Strümpfer

et al. 2012

The Journal of Chemical Physics

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In many physical, chemical, and biological systems energy and charge transfer processes are of utmost importance. To determine the influence of the environment on these transport processes, equilibrium molecular dynamics simulations become more and more popular. From these simulations, one usually determines the thermal fluctuations of certain energy gaps, which are then either used to perform ensemble-averaged wave packet simulations, also called Ehrenfest dynamics, or to employ a density matrix approach via spectral densities. These two approaches are analyzed through energy gap fluctuations that are generated to correspond to a predetermined spectral density. Subsequently, density matrix and wave packet simulations are compared through population dynamics and absorption spectra for different parameter regimes. Furthermore, a previously proposed approach to enforce the correct long-time behavior in the wave packet simulations is probed and an improvement is proposed.

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“…As discussed earlier, this deficiency originates from the classical treatment of the phonon bath and cannot be improved by reorganization correction. Based on previous work by Bastida et al, 79 Aghtar et al 29 have introduced a correction factor that leads to the fulfillment of detailed balance. Although their scheme gives the correct thermal equilibrium distribution, it overestimates dephasing rates.…”

Section: A Population Dynamicsmentioning

confidence: 99%

A stochastic reorganizational bath model for electronic energy transfer

Fujita

Huh

Aspuru‐Guzik

2014

The Journal of Chemical Physics

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The fluctuations of optical gap induced by the environment play crucial roles in electronic energy transfer dynamics. One of the simplest approaches to incorporate such fluctuations in energy transfer dynamics is the well known Haken-Strobl-Reineker model, in which the energy-gap fluctuation is approximated as a white noise. Recently, several groups have employed molecular dynamics simulations and excited-state calculations in conjunction to take the thermal fluctuation of excitation energies into account. Here, we discuss a rigorous connection between the stochastic and the atomistic bath models. If the phonon bath is treated classically, time evolution of the exciton-phonon system can be described by Ehrenfest dynamics. To establish the relationship between the stochastic and atomistic bath models, we employ a projection operator technique to derive the generalized Langevin equations for the energy-gap fluctuations. The stochastic bath model can be obtained as an approximation of the atomistic Ehrenfest equations via the generalized Langevin approach. Based on the connection, we propose a novel scheme to correct reorganization effects within the framework of stochastic models. The proposed scheme provides a better description of the population dynamics especially in the regime of strong exciton-phonon coupling. Finally, we discuss the effect of the bath reorganization in the absorption and fluorescence spectra of ideal J-aggregates in terms of the Stokes shifts. For this purpose, we introduce a simple relationship that relates the reorganization contribution to the Stokes shifts - the reorganization shift - to three parameters: the monomer reorganization energy, the relaxation time of the optical gap, and the exciton delocalization length. This simple relationship allows one to classify the origin of the Stokes shifts in molecular aggregates

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A modified Ehrenfest method that achieves Boltzmann quantum state populations

Cited by 51 publications

References 27 publications

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

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

Juxtaposing density matrix and classical path-based wave packet dynamics

A stochastic reorganizational bath model for electronic energy transfer

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