First-principles Calculation of Atomic Location of 3d Transition Metal Elements in B2-type Ti-Ni Alloy*

Ti-Ni alloy is one of the widely-used shape memory alloys and its martensitic transformation can be controlled by introducing 3d transition metal (3d-TM) elements. To clarify the effects of 3d-TM elements, Nakata et al., investigated atomic location of 3d-TM by using the ALCHEMI technique [1], and found that Fe and Co (Sc) favor Ni (Ti) site. The location of V, Cr, Mn and Cu depends on the Ti-Ni ratio. In this paper, we perform first-principles calculations on these alloy systems, and discuss electronic origin of the location of 3d-TM in B2-type Ti-Ni. For the present calculations, we use VASP code [2] and calculate formation energy of substitutional 3d-TM in B2-type TiNi. It is found that Cr, Mn, Fe and Co favor Ni site, and Sc favors Ti site. V and Cu can replace both sites. We also perform COHP analysis [3] and it is found that the chemical trend of the atomic location can be understood from the viewpoint of chemical bonding between 3d-TM and neighboring Ti and Ni.
[1] Y. Nakata et al., Mat. Trans. JIM 32 (1991) 580, ibid 1120.
[2] G. Kresse and J. Furthmueller, Comput. Mat. Sci. 6 (1996) 15.
[3] R. Dronskowski and P. E. Bloechl, J. Phys. Chem. 97 1993) 8617.