Mixed quantum-classical simulations of charge transport in organic materials: Numerical benchmark of the Su-Schrieffer-Heeger model

摘要

The electron-phonon coupling is critical in determining the intrinsic charge carrier and exciton transport properties in organic materials. In this study, we consider a Su-Schrieffer-Heeger (SSH) model for molecular crystals, and perform numerical benchmark studies for different strategies of simulating the mixed quantum-classical dynamics. These methods, which differ in the selection of initial conditions and the representation used to solve the time evolution of the quantum carriers, are shown to yield similar equilibrium diffusion properties. A hybrid approach combining molecular dynamics simulations of nuclear motion and quantum-chemical calculations of the electronic Hamiltonian at each geometric configuration appears as an attractive strategy to model charge dynamics in large size systems “on the fly,” yet it relies on the assumption that the quantum carriers do not impact the nuclear dynamics. We find that such an approximation systematically results in overestimated charge-carrier mobilities, with the associated error being negligible when the room-temperature mobility exceeds ∼4.8 cm2/Vs (∼0.14 cm2/Vs) in one-dimensional (two-dimensional) crystals. © 2011 American Institute of Physics Article Outline INTRODUCTION THEORETICAL METHODOLOGY RESULTS AND DISCUSSION Role of the realization average in the ES strategy Role of the initial charge extension in the WF and the DM strategies Comparison between the ES, the WF, and the DM strategies Role of feedback in the nonlocal Hamiltonian Role of feedback in the local Hamiltonian CONCLUSION