Analysis of the electronic structure of intermetallic compounds, and application to structural defects in B2 phases

A general calculational scheme is described to analyse the stability and the defect energetics of intermetallic compounds in terms of a chemical language for the bonding properties. To do this, the contribution to the total energy of bonding and antibonding hybrid states between atom-localized orbitals is determined. This scheme is used to test the general assumption that in the B2 phases TMAl (where TM is a transition metal atom) the defect energetics may be mainly traced back to the properties of the TM-d-Al-sp bonds. By calculations for FeAl, CoAl and NiAl it is shown that this simple conception is not valid and that the defect energetics are determined by the net effect of many competing energetic contributions of comparable size.