Electronic structure of B2-type Ti-Ni-Fe alloys exhibiting second-order-like structural transformation

We have calculated electronic structure of B2-type Ti-(50 - x)Ni-xFe (0 ≤ x ≤ 28) alloys in order to understand the concentration dependence of the phase stability of the B2-type structure in this system. The Fermi surface of each alloy shows a nesting with a sharp peak of generalized susceptibility χ(q) at a nesting vector of q = [ζζ0]2π/a. The value of ζ at the peak position decreases linearly as the Fe content increases. On the contrary, the peak height of χ(q) does not change monotonically but shows a maximum value for Ti-44Ni-6Fe alloy. This result is consistent with the experimental results obtained by resistivity and specific heat measurements. In addition, we found that although the χ(q) shows a local maximum near 1/3[110]2π/a in Ti-44Ni-6Fe alloy, it shows a saddle point near 1/3[110]2π/a in TiNi.