Molecular Dynamics Study on Structural Relaxation Processes in Amorphous Germanium

The structural relaxation of amorphous germanium was examined by molecular dynamics simulations based on the empirical Tersoff interatomic potential. Although the Tersoff potential overestimated both the melting and glass transition temperatures, it was able to reproduce the structural relaxation behavior. The potential energy decreases with thermal annealing below the glass transition temperature, but occasionally increases during structural relaxation. The mean square displacement of atoms also increases in these periods. These changes were attributed to cooperative atomic motion during the structural relaxation. Atomic trajectories revealed that structural changes are induced by spatially- and temporally-inhomogeneous atomic motions: atomically mobile and immobile regions coexist during structural relaxation.