Computer analysis on the structure of low-density and high-density amorphous germanium

The structures of low-density and high-density amorphous germanium are studied, using the order-N non-orthogonal tight-binding molecular dynamics method, where N is the number of atoms, implemented in our recent work. The initial amorphous configuration is taken from the results of a glass transition simulation performed in a separate work, with N = 512. From this initial configuration, we gradually increase the density of the system. From detailed analyses of the two-body distribution function and the bond-angle distribution function, we deduce the structural change in amorphous germanium with increase of the density. Through these analyses, we find that amorphous germanium transforms from a tetrahedrally-coordinated amorphous structure at low density to a β-Sn-like amorphous structure at high density.