Electronic structure and stability of intermetallic compounds in the Ti–Ni System

For the systematical understanding of the stability of martensitic phases and precipitates which appear in Ti–Ni shape memory alloys, we made a first principle electronic structure calculation of them by using the tight-binding linear muffin-tin orbital method in the atomic sphere approximation (TB-LMTO-ASA). The obtained results are the following: (1)the total electronic density of state (DOS) at the Fermi energy D(εF) of TiNi decreases as the successive B2→R→B19′ transformation proceeds; (2) when the number of valence electrons increases, D(εF) of the R-phase increases but that of the B19-phase decreases; (3) D(εF) of Ti3Ni4 decreases as the number of valence electrons decreases and that of TiNi2 decreases as the number of valence electrons increases. By comparing these results with experimentally obtained results, we derived a criterion that phases appearing in Ti–Ni system tend to become stable at 0 K as D(εF) decreases.