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<=q x<=q 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 (chi)(q) at a nesting vector of q= [(zeta)(zata) 0]2(pi)/a. The value of (zeta) at the peak position decreases linearly as the Fe content increases. On the contrary, the peak height of (chi)(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 (chi)(q) shows a local maximum near 1/3[110]2(pi)/a in Ti–44Ni–6Fe alloy, it shows a saddle point near 1/3[110]2(pi)/a in TiNi.