ELECTRONIC-STRUCTURE AND PHASE-STABILITY STUDY IN THE NI-TI SYSTEM

We present the results of a phase stability study in the Ni-Ti system. In particular, the formation energies of the three NiTi2, NiTi, and N i3Ti compounds have been calculated using the full potential linear-mu ffin-tinorbital method. The correlation between the electronic concent ration and the crystal structure is interpreted in terms of the fillin g of bonding states for the Ni3Ti compound. Two sets of effective clus ter interactions are determined allowing us to include bcc- and fee-ba sed solid solutions in the phase stability analysis. Ordering effects are treated by means of the cluster variation method. An attempt to ca lculate the composition-temperature phase diagram of the Ni-Ti system is proposed.