THERMODYNAMICS OF THE NICKEL-TITANIUM SYSTEM - A TIGHT-BINDING-BOND APPROACH

Tight-binding electronic band structure calculations are combined with a free-energy expression from the cluster variation method to study phase equilibria in the Ni-Ti system. The effective pair interactions used in the cluster variation calculations are evaluated by means of the generalized perturbation method. The configurational entropy for disordered solutions and for ordered compounds are obtained using the tetrahedron approximation of the cluster variation method. A phase diagram is calculated and is found to be in good agreement with the experimental one.