A model tight-binding Hamiltonian including off-diagonal disorder and Hartree-Fock electronic self-consistency is used to calculate the enthalpies of formation of the Mo-Cr, Mo-Nb, and Mo-Ta alloys. The approach combines the coherent-potential approximation, the generalized perturbation method, and the cluster-variation method. The model is also used to calculate the phase diagram and the equilibrium activities for the Mo-Cr system.

• Received 25 March 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.253