Volume of formation and electronic configuration in dilute alloys

A method is presented to relate the volume of formation to the electronic configuration of impurities in metals. The electronic configuration determines the effective size of the impurity through a modified ThomasFermi-Dirac model combined with elasticity theory. The size of the impurity determines the macroscopic volume change in the crystal, and the electronic configuration can be varied to fit the experimental volume of formation. Alloys of mainly transition metals are studied. The general conclusion of the work is that the charge transfer deduced from the changes in electronic configuration agrees with the expectations of the electronegativity scales, except for a few exceptions. For most of the alloys studied the changes consist of reoccupation of d and non-d levels at each site, maintaining the local neutrality. Only in a few cases were ionic configurations found, and the degree of ionicity was very small.