First-principles study of the elastic properties and electronic structure of NiTi, CoTi and FeTi

First-principles total-energy electronic structure calculations bas ed on t he full-potential linearized augmented plane-wave method have been carried out to study the elastic properties and electronic structure of NiTi, CoTi and FeTi. The calculated values for the equilibrium lattice constants and e lastic properties are generally in good agreement with experiments. From th e calculated results, it is found that the anisotropy factors are ordered a s follows NiTi>CoTi> FeTi and the shear moduli C' are ordered as FeTi> CoTi > NiTi. The close relationship between the anisotropy factor and the stabil ity of the B2-type Ti-based alloys has been discussed. It is shown that a l ower anisotropy factor is an important factor for the existence of the B19' structure in NiTi. The total electron densities of states (DOSs) and the d DOS of the Ti element of the three alloys have been calculated. The stabil ities of NiTi, CoTi and FeTi have been discussed on the basis of the presen t results on the electronic structure calculations.