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 the 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 elastic properties are generally in good agreement with experiments. From the calculated results, it is found that the anisotropy factors are ordered as follows NiTi>CoTi> FeTi and the shear moduli C' are ordered as FeTi> CoTi> NiTi. The close relationship between the anisotropy factor and the stability of the B2-type Ti-based alloys has been discussed. It is shown that a lower 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 stabilities of NiTi, CoTi and FeTi have been discussed on the basis of the present results on the electronic structure calculations.