On the alternatives for bath correlators and spectral densities from mixed quantum-classical simulations

Valleau, Stéphanie; Eisfeld, Alexander; Aspuru‐Guzik, Alán

doi:10.1063/1.4769079

Cited by 144 publications

(274 citation statements)

References 54 publications

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“…The reorganization energies 658.7 and 719.9 cm −1 for syn and anti monomers, respectively, were calculated as E R = ∞ 0 dω j(ω)/ω. These values are larger than those calculated from the spectral densities with the standard prefactor [65] in our previous paper [22]. Our MD/TDDFT calculations imply that the reorganization energies of the BChl d in the roll is larger than that in solvent (69 cm −1 ) [66].…”

Section: A Spectral Densitiescontrasting

confidence: 63%

“…[65] In the obtained temperature-independent spectral density, Figure 2, the strong peaks around 1600 to 2000 cm −1 are due to internal vibrational modes of the BChl, while the low-frequency region is ascribed to intermolecular interactions between the BChl molecules. The reorganization energies 658.7 and 719.9 cm −1 for syn and anti monomers, respectively, were calculated as E R = ∞ 0 dω j(ω)/ω.…”

Section: A Spectral Densitiesmentioning

confidence: 90%

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Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

et al. 2014

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We present a theoretical study of excitation dynamics in the chlorosome antenna complex of green photosynthetic bacteria based on a recently proposed model for the molecular assembly. Our model for the excitation energy transfer (EET) throughout the antenna combines a stochastic time propagation of the excitonic wave function with molecular dynamics simulations of the supramolecular structure, and electronic structure calculations of the excited states. We characterized the optical properties of the chlorosome with absorption, circular dichroism and fluorescence polarization anisotropy decay spectra. The simulation results for the excitation dynamics reveal a detailed picture of the EET in the chlorosome. Coherent energy transfer is significant only for the first 50 fs after the initial excitation, and the wavelike motion of the exciton is completely damped at 100 fs. Characteristic time constants of incoherent energy transfer, subsequently, vary from 1 ps to several tens of ps. We assign the time scales of the EET to specific physical processes by comparing our results with the data obtained from time-resolved spectroscopy experiments.

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Section: A Spectral Densitiescontrasting

confidence: 63%

Section: A Spectral Densitiesmentioning

confidence: 90%

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

et al. 2014

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“…On the other hand, in large e-h separation, the electron and hole interact with a phonon bath individually. We need to treat N state-specific SDs for CT states, which is computationally expensive to calculate all of them from mixed quantum/classical simulations [67]. Instead, we define an e-h distance dependent SD, j(R), from Frenkel ( j f ), electron ( j e ), and hole ( j h ) SDs.…”

Section: Appendix B: Spectral Densitiesmentioning

confidence: 99%

“…Both of them are calculated from a spectral density j n (ω) for the nth diabatic state [62,65]. The spectral densities [66,67] have been obtained by combing molecular dynamics simulations for the DNTT crystal with excited-state calculations using time-dependent density functional theory at B3LYP/6-31G* level. The details for calculating spectral densities are presented in the Appendix B.…”

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confidence: 99%

Coherent Dynamics of Mixed Frenkel and Charge-Transfer Excitons in Dinaphtho[2,3-b:2′3′-f]thieno[3,2-b]-thiophene Thin Films: The Importance of Hole Delocalization

Fujita

Atahan-Evrenk

Sawaya

et al. 2016

J. Phys. Chem. Lett.

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Charge transfer states in organic semiconductors play crucial roles in processes such as singlet fission and exciton dissociation at donor/acceptor interfaces. Recently, a time-resolved spectroscopy study of dinaphtho [2,3-b:2 ′ 3 ′ -f]thieno[3,2-b]-thiophene (DNTT) thin films provided evidence for the formation of mixed Frenkel and charge-transfer excitons after the photoexcitation. Here we investigate optical properties and excitation dynamics of the DNTT thin films by combining ab initio calculations and a stochastic Schrödinger equation. Our theory predicts that the low-energy Frenkel exciton band consists of 8 to 47% CT character. The quantum dynamics simulations show coherent dynamics of Frenkel and CT states in 50 fs after the optical excitation. We demonstrate the role of charge delocalization and localization in the mixing of CT states with Frenkel excitons as well as the role of their decoherence.Organic semiconductors (OSCs) are widely investigated as candidates for inexpensive and flexible materials for photovoltaics and other optoelectronic applications. [1][2][3]. In recent years, new OSCs have been designed and improved through computational modeling [4][5][6] and virtual high-throughput screening [7][8][9]. Modeling energy and charge transport properties is also essential for understanding structure-property relationships and thus for rationally designing novel OSCs [10][11][12][13][14][15][16].The low-energy optical excitations in OSCs lead to the formation of a bound electron-hole (e-h) pair, a Frenkel exciton. Excitonic properties of organic crystals are substantially different from those of isolated molecules, owing to excitonic couplings, near-field interactions between electronic transitions [17][18][19][20]. Interactions with a charge-transfer (CT) statea state in which the electron and hole are located on spatially separated regions-can also affect the optical properties of an exciton, as has been demonstrated by several theoretical studies [21][22][23][24][25][26]. Experimentally, the degree of CT character has been studied by momentum-dependent electron-loss spectroscopy [27][28][29] or electroabsorption spectroscopy [30][31][32]. CT states can act as precursors for interfacial CT states [33][34][35]; mixing of CT states with Frenkel excitons would facilitate charge separation in photovoltaic materials. They have also gained recent attention due to their relevance to singlet fission [36][37][38], in which singlet to triplet conversion can proceed via sequential CT steps [39][40][41].Here we focus on dinaphtho[2,3-b:, a p-type OSC originally introduced by Takimiya and co-workers [42]. DNTT and its derivatives [5,[43][44][45][46][47][48][49] have gained attention due to their high hole mobility values and air stability. A recent time-resolved spectroscopy study by Ishino et al. [48] concludes that mixed Frenkel and CT excitons are formed after the optical excitation. Although the degree of CT character in excited states has been reported as described in the earlier paragraph, its role in...

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“…As mentioned previously, in recent years, exciton-phonon interactions have been treated at the atomistic level by combining molecular dynamics simulations and excited-state calculations. [53][54][55][56][57][58] From these simulations, one can perform ensemble-averaged wavepacket dynamics, 29, 59-61 also called Ehrenfest dynamics, or extract a spectral density 62 for its use in a quantum master equation.…”

Section: Introductionmentioning

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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On the alternatives for bath correlators and spectral densities from mixed quantum-classical simulations

Cited by 144 publications

References 54 publications

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

Theoretical characterization of excitation energy transfer in chlorosome light-harvesting antennae from green sulfur bacteria

Coherent Dynamics of Mixed Frenkel and Charge-Transfer Excitons in Dinaphtho[2,3-b:2′3′-f]thieno[3,2-b]-thiophene Thin Films: The Importance of Hole Delocalization

A stochastic reorganizational bath model for electronic energy transfer

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