Thermodynamics of constitutional and thermal point defects in B2N1-xAlx

In view of the discussion on whether or not constitutional vacancies occur in B2 intermetallic compounds, a recently proposed model for point-defect formation in such compounds has been elaborated. In contrast with the results obtained by Ren and Otsuka (2000, Phil. Mag. A, 80, 467) it is shown that the statistical thermodynamic model applied to the available experimental data for B2 Ni1-xAlx (vacancy concentrations as function of composition and temperature, activity data and enthalpy of formation data, both as functions of composition) does not lead to the conclusion that constitutional vacancies do not exist. In fact, all available data, except for the vacancy concentrations experimentally determined by Kogachi et al., are found to be fully consistent with the triple-defect model.