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 Å can be explained in terms of void correlations. In the intermediate self-scattering function, i.e., the density fluctuation correlation, classical behavior, a and b regimes, is found. We also observe the plateau in the b 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!, b and a regimes. We have also shown that the increase in heterogeneity can be understood in terms of relaxations.