Non-adiabatic molecular dynamics simulation combining explicit electronic struc- ture calculations (e.g. CASSCF or TDDFT) with classical dynamics (e.g. Ehrenfest, Surface hopping (SH)) are computationally extremely demanding and can be presently done only for small systems (10-100 atoms) and over short time scales (10-100 fs) [1,2]. While this is of- ten sufficient to describe ultrafast photochemical reactions in the gas phase, there are a host of non-adiabatic processes where substantially larger system sizes and longer time scales are required, for instance to describe exciton[3,4] and charge transport (CT)[5,6] in organic semi- conductors (OS), redox proteins and DNA[7] and photoelectrodes. Here we report on the implementation and application of a fast SH method that we have developed to address these fascinating problems [8,9].<br/>We apply our fast SH method to charge transport in 1D chains of organic molecules forming organic semiconductors [8], specifically we compute the temperature dependence of electron hole mobility along the chains. For small ratios of electronic coupling vs reorganisation energy (Hab/lambda &lt;&lt; 1), we observe a crossover from thermally activated to band-like transport as the temperature is increased, whereas for large ratios (Hab/lambda ≈ 0.5) the thermally activated transport regime disappears and the mobility decays according to a power-law for all temperatures. We will also outline how our method can be made linear scaling, which will give us access to simulation of CT in 2D and 3D materials.

Fragment orbital-based surface hopping for simulation of charge carrier transport in materials and biomolecules

253rd National Meeting (2017)

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