Current-transient Simulation of polyethylene by first principles

Fast transient current in polymeric insulator is widely interpreted in terms of semi-phenomenological Scher-Montroll (S-M) theory, owing to the somewhat satisfactory fitting to the experimental data. However, from a theoretical point of view, it is questionable whether this model can be applied to carrier transfer in insulators where polaronic effect plays an important role. In this contribution, hole transfer in amorphous polyethylene (PE) is simulated with the combination of molecular dynamics, quantum chemical, and kinetic Monte Carlo calculations, without adopting semi-empirical or phenomenological models. Hole hopping rates were computed with the approximate form of the Fermi's golden rule rate kernel that takes into account the coupling between carriers and molecular vibrational modes. Current waveforms were computed from the trajectories of holes. Computed current waveforms exhibit the so called anomalous diffusion properties, and moreover, they indeed roughly obey the well-known “universality” predicted by S-M theory. It is also shown that, in line with experimental findings, the slopes of the S-M plot deviates from the prediction of S-M theory.