Ordered intermetallic compounds draw great interest at the present time because of both possiblernapplications and fundamental scientific importance. The scientific interest is derived from thernrecognition that many intermetallics exhibit considerable ranges of nonstoichiometry whichrncorrespond to the presence of constitutional point defects which are temperature independent.rnAdditional to these constitutional point defects thermally activated point defects can occur. Therntotal defect structure (i.e. the types and the concentrations of the point defects) determinesrnimportant properties of the intermetallic compounds (e.g. all diffusion dependent properties).rnHence, for understanding and control of these properties a detailed knowledge of the defectrnstructure in intermetallic compounds as function of composition and temperature within thernhomogeneity range of the compounds is a prerequisite. This thesis is aimed at formulating arnmodel which can be used to calculating the ordering energy parameters Î”HAB and Î”HBâ–¡, and thernconcentration of vacancy (z) and the concentration of Antistructure Defect as a function of therncomposition parameter Ï‡ and the temperature T. The ordering energy is related to but differentrnfrom the formation energy, because the former is the energy change from the disordered alloyrnAB to the ordered alloy AB, while the latter is the energy change from the pure metals A and Brnto the ordered AB. Having obtained the model parameters (note that these are H ij and S ij forrnthe fitting of the vacancy concentration and hij and sij for the fitting of the thermodynamicrnproperties, respectively), the temperature dependence of the vacancy concentration can also berndetermined.