THEORETICAL-ANALYSIS OF POSSIBLE MARTENSITIC PHASES IN TITANIUM NICKELIDE

The concept or co-operetive thermal vibrations in crystals is applied here for an independent analysis of a system of martensitic phase tran sitions in titanium nickelide (NiTi). In addition to the orthorhombic B19 phase. which is well known for NiTi, a trigonal and a monoclinic p hase - have been produced and are analyzed in detail. The calculated a nd experimental neutron diffraction patterns obtained for monoclinic a nd trigonal phases show a good agreement. The obtained structure of th e monoclinic phase is absolutely different from the B19' structure des cribed in tile literature. Finally. more emphasis is placed on some co mplicated problems associated with a detailed identification of the tr igonal phase structure.