Molecular-dynamics simulation of solitary waves in polyethylene

We carry out molecular-dynamics simulation studies of two types of solitonlike defects, namely, twist elongation (TE) and twist compression (TC) of a polyethylene chain surrounded by a rigid crystal environment. We show that the TE can propagate smoothly with a wide range of velocities, but that in contrast the TC is easy to collapse into a sharply localized immobile defect. We observe that a free chain end has an attractive force to the TE soliton, which can be annihilated after interactions with the chain end. We briefly investigate the effects of thermal disorder on the soliton excitations.