Electronic structure of B2-type Ti–(50 − x)Ni–xFe and Ti–(50 − x)Pd–xFe alloys exhibiting incommensurate diffuse scattering

We have calculated the electronic structure of B2-type Ti–(50 − x)Ni–xFe (0 ≤ x ≤ 28 at.%) and Ti–(50 − x)Pd–xFe (0 ≤ x ≤ 22 at.%) alloys in order to understand the origin of diffuse scattering appearing in these systems, and the stability of the B2-type structure. For both systems, the Fermi surface of each alloy shows nesting with a sharp peak in the generalized susceptibility χ(q) at a nesting vector of qn = [ζn ζn 0]2π/a. The value of ζn of the peak position decreases linearly as the Fe content increases. In addition, the peak of χ(q) decreases as the Fe content increases except for Ti–(50 − x)Ni–xFe with x ≤ 4 at.%. These results suggest that the position of diffuse scattering shifts towards its nearest fundamental reflection of the B2-phase as the Fe content increases and that the stability of the B2-phase increases with increasing Fe content. These suggestions are in good agreement with experimental results reported until now.