Benchmarking calculations of spectral densities for the diagonal and nondiagonal exciton-phonon coupling of tetracene crystal

Abstract

The spectral densities of diagonal and nondiagonal exciton-phonon (e-p) coupling for tetracene crystal have been calculated by the harmonic oscillator (HO) model and ground-state MD-based approaches. We find that classical MD-based approaches overestimate the coupling of exciton with high-frequency vibrational modes and predict the strongest e-p coupling appeared above 1500 cm(-1) whereas HO model and AIMD-based approach predict it appeared at similar to 1400 cm(-1). Additionally, the calculated spectral densities of nondiagonal e-p coupling for three different dimers show that they are continuously distributed in the range of 0-150 cm(-1) and are 2-3 order of magnitude smaller than the maxima of diagonal e-p coupling. (C) 2017 Elsevier B.V. All rights reserved.