Vibrations and electronic states in a model amorphous metal

Abstract

Calculations are presented of the electronic and vibrational properties of a periodic, 500-atom unit cell model of the structure of an amorphous metal. We treat both the effects of topological and quantitative disorder, the latter being due to variations of interatomic force constants or hopping matrix elements. Topological structure in the model is characterized in terms of the radial distribution function, near-neighbor ring statistics, and the static scattering function $I\left(Q\right)\mathrm{}$. Calculations are presented of the vibrational density of states, the neutron scattering law $S(Q,\omega )$, and the electronic density of states. In these calculations, the structural disorder is treated exactly, within the framework of simplified models retaining only first-nearest-neighbor interactions. Despite these approximations we expect that the vibrational structure will accurately characterize experimental neutron scattering results in amorphous metals such as PdSi alloys. We find that topological disorder alone does not destroy gross features in the density of states. However, quantitative disorder broadens the electronic spectra and washes out structure in the vibrational density of states almost completely.