The vibrational density of states of amorphous silicon and germanium from a small cluster model

Abstract

A small crystalline cluster model of the vibrational spectrum of amorphous silicon and germanium has been developed. It has boundary conditions on the surface atoms simulating the imbedding of the cluster in a disordered medium. The vibrational spectrum obtained has the same gross three-peaked structure observed in the infrared absorption data for these materials. Good agreement with the positions of the high and low frequency peaks was obtained. However, the calculated frequency of the central peak was 20% higher than the observed frequency.