CALCULATION OF THE ELECTRONIC-STRUCTURE OF THE AMORPHOUS PD80SI20 SYSTEM

A basis of s, p and orbitals on Pd and s and p orbitals on Si sites is used to calculate the electronic density of states per unit cell of the Pd 3Si crystal and formula unit densities of states for different regions of two network models of the amorphous Pd80Si20 system. In contrast to the results of previous calculations which involved simpler model Hamiltonians for the system, it has been found that the differences in the electronic structure which reflect the local topological environment are rather modest and are certainly less prominent than those obtained in the study of three- and fourfold-coordinated amorphous semiconductors. The results compare favourably with available photoemission data and it is suggested that the s valence features of silicon may be a sensitive probe of topology in the Pd80Si20 system. The local density of states at the silicon site is spread over a wide range of energies and contributes significantly to the Fermi level density of states, thus providing a clue to the strength and transport properties of these amorphous alloys.