A molecular dynamics study of amorphous selenium

Abstract

The structure of amorphous selenium has been studied using molecular dynamics. Ten chains of selenium consisting of 30 atoms each have been generated by a new algorithm with glass density as a criterion. A covalent bond has been simulated using harmonic potential and non-bonded closed shell interactions have been treated using Lennard-Jones potentials both for intra-and inter-chain atoms. Good agreement of bond distances, bond angles and nearest neighbour coordinations with experimental data has been observed. Absence of any preferred dihedral angle has been noticed. Diffusion of selenium has been interpreted as a result of coupled motion of atoms in the chains whose overall dynamics is considered as jiggling. It has been shown that the activation barrier for this kind of a displacement is fairly low, although atomic displacements give a diffusion constant of around 2×10^-7 cm²/s at 200 K.