ELECTRONIC-STRUCTURE OF B2-NITI AND B2-PDTI

The electronic structure of B2-phase NiTi and PdTi is determined by means of the self-consistent Linearized Augmented Plane Wave (LAPW) method. The bandstructures, local densities of states and electron densities for the two compounds are compared and the differences analyzed. The calculated broadened DOS show close resemblance with measured photoelectron spectra. Accurate calculations of the Fermi surface and some Fermi surface-related properties are also presented. We investigate the topology of the Fermi surface and calculate the generalized susceptibility of non-interacting electrons and, approximately, the electron-phonon contribution to the dynamical matrix of phonons, in order to estimate the influence of nesting regions on the electron-phonon coupling, thus establishing a relation between the electronic structure and the martensitic transformations of these compounds. The calculations suggest that the appearance of ''bottle-necks'' in the Fermi surface of PdTi may be responsible for the different transformational behaviour of these two alloys.