Structure and relaxation in liquid and amorphous selenium

We report a molecular dynamics simulation of selenium, described by a three-body interaction. The temperatures Tg and Tc and the structural properties are in agreement with experiment. The mean nearest neighbor coordination number is 2.1. A small prepeak at about 1 ^-1 can be explained in terms of void correlations. In the intermediate self-scattering function, i.e., the density fluctuation correlation, classical behavior, α and β regimes, is found. We also observe the plateau in the β regime below Tg. In a second step, we investigated the heterogeneous and/or homogeneous behavior of the relaxations. At both short and long times the relaxations are homogeneous (or weakly heterogeneous). In the intermediate time scale, lowering the temperature increases the heterogeneity. We connect these different domains to the vibrational (ballistic), β and α regimes. We have also shown that the increase in heterogeneity can be understood in terms of relaxations.