Metabasin dynamics of supercooled polymer melt

We employ molecular dynamic simulation to investigate metabasin dynamics for supercooled polymer melt. We find that, in a small system, the α-relaxation process is composed of a few crossing events that the monomers hops from one metabasin to another. Each crossing event is very rapid and involves a democratic movement of many particles, whereas such collective motion is not string-like. Evaluation on the contributions of metabasin exploration and democratic movement shows that the structural relaxation is mostly governed by the latter. Our calculated results show that the metabasin-metabasin transitions are not the main reason of spatially dynamical heterogeneity. It is different from the binary Lennard-Jones mixture model in which the metabasin-metabasin transitions are relevant for the spatially dynamical heterogeneity.