Cluster variation method approach to estimating vacancy properties in B2 type ordered NiAl and NiFeAl alloys

To compute the vacancy concentration in B2 type ordered NiAl and NiFeAl alloys, a new calculation technique based on the cluster variation method (CVM) was developed. The critical condition for finding the solution is prescribed as the vacancy concentration at which the chemical potential in the alloys vanishes. Using this method together with a set of appropriate interaction parameters for each nearest or second nearest neighbouring atom-atom or atom-vacancy pair, we can easily and definitely calculate the vacancy concentration in these alloy systems, in contrast to the conventional method which is more sophisticated since it deals with an open system with respect to the number of vacancies. Comparisons between the calculated results and available experimental data for the vacancy properties of these alloy systems are made.