Structural and electronic properties of the martensitic alloys TiNi, TiPd, and TiPt

Abstract

The electronic and structural properties for TiNi, TiPd, and TiPt are studied using first-principles total energy calculations. For each alloy, the structural parameters for a few structural phases are found from energy and force calculations. In each case, we found that the ground state martensitic phase (B19/B19Ј) is indeed lower in energy than the high temperature B2 phase. In all three alloys, the lowering in energy of the B19/B19Ј structure is associated with the electronic properties such as lowering of the density of states at the Fermi level at the Ti site, and the broadening of the transition-metal d bands in the B19/B19Ј phase compared with the B2 phase. ͓S0163-1829͑97͒00331-7͔

Theoretical prediction and experimental study of a ferromagnetic shape memory alloy:Ga2MnNi

“…23 The numbers in bracket indicate δE tot and T M in meV/atom and K, respectively, as taken from Ref. 23. Similar trend is obtained for Ni excess Ni-Mn-Ga. 21,24,28 In Fig.…”

“…This expression should be generally valid, and this indeed seems so for TiNi (45, 333), TiPd (95, 783) and TiPt (155, 1343). 23 The numbers in bracket indicate δE tot and T M in meV/atom and K, respectively, as taken from Ref. 23.…”

First-principles study of the structural energetics of PdTi and PtTi

“…The free-electron like sp bands are very broad, and play little role in the bonding except to donate some electrons to the Ti-d band. The large strain involved in the B2 − B19 transition means that the Fermi surfaces are quite different (B19 having the lowest DOS at E F [16]) and this transition cannot be related directly to the band structure. By contrast, the B19-B19 ′ transition is accompanied by the opening of a pseudogap at the Fermi level, a typical signature of increased stability.…”

“…For the distortion to be frozen in, we choose the eigenvector that gives the space group P mma of the B19 structure ( Figure 2). The unit cell is orthorhombic, with lattice parameters a, b and c, two Wyckoff positions occupied by Ti and Pd/Pt Computed structural parameters and total energies of PdTi and PtTi in the B19 and B19 ′ structures, compared with the computed L10 structure, the computed bco structure, the experimental B19 structure, with previous calculations [16] and with two special B19 structures with b/a and c/a corresponding to ideal hcp and B2 (bcc) structures. Volume is given in A 3 /formula unit, and energy in eV/atom.…”

Theoretical Investigations of Ti-Based Binary Shape Memory Alloys

“…To investigate Martensitic phase transformation from the electronic point of view, Ye et al [3] have used first principles total energy calculations to show some interesting correlations between the relative stability of B2 and (B19/B19') phases with the electronic structure for TiNi, TiPd and TiPt alloys.…”