Preparation, structure, dynamics, and energetics of amorphous silicon: A molecular-dynamics study

Abstract

The preparation of amorphous silicon by molecular-dynamics simulations employing the Stillinger-Weber Si potential, via direct slow cooling from the melt, is described. It is shown that previous failures to obtain amorphous Si using these interaction potentials are of kinetic origin, i.e., related to the quench rate employed. The amorphous silicon sample which we prepared exhibits structural and dynamical properties in good agreement with available experimental data for the static structure factor and phonon density of states. Detailed analyses of the structure, including distributions of bond and dihedral angles and ring statistics, and energetics, including the determination of effective temperatures for n-fold-coordinated atoms (n=3–5) and estimates of the formation energy of coordination defects (i.e., n≠4) are presented. The lack of medium-range order, measured via correlation between dihedral angles associated with adjacent bonds, is discussed.