The electronic structure of NiAl and NiSi

Abstract
A study of the electronic structure of NiSi and NiAl employing electron spectroscopies and theoretical calculations is presented. Experimental results, obtained with X-ray photoemission and bremsstrahlung isochromat spectroscopy, are interpreted by means of density of states and matrix element calculations for the compounds in their real crystal structure. This gives a detailed picture of the electronic states over the whole bonding-antibonding region below and above the Fermi level. Cluster calculations based on a molecular orbital approach for NiAl provide further insight into the bonding characteristics of the states of various symmetries. The authors find that the simple d-p bonding scheme used so far for the silicides, in which the metal d states are referred to as 'non-bonding', needs revision.