Electronic structure and stability of intermetallic compounds in the Ti-NiSystem

For the systematical understanding of the stability of martensitic phases a nd precipitates which appear in Ti-Ni shape memory alloys, we made a first principle electronic structure calculation of them by using the tight-bindi ng linear muffin;tin orbital method in the atomic sphere approximation (TB- LMTO-ASA). The obtained results are the following: (I)the total electronic density of state (DOS) at the Fermi energy D(epsilon(F)) of TiNi decreases as the successive B2 --> R --> B19' transformation proceeds; (2) when the n umber of valence electrons increases, D(epsilon(F)) of the R-phase increase s but that of the B19-phase decreases; (3) D(epsilon(F)) of Ti3Ni4 decrease s as the number of valence electrons decreases and that of TiNi, decreases as the number of valence electrons increases. By comparing these results wi th experimentally obtained results, we derived a criterion that phases appe aring in Ti-Ni system tend to become stable at 0 K as D(epsilon(F)) decreas es. (C) 1999 Elsevier Science S.A. All rights reserved.