Site preference and elastic properties of Fe-, Co-, and Cu-doped Ni2MnCa shape memory alloys from first principles.

The site preference and elastic properties of Fe-, Co-, and Cu-doped Ni2MnGa alloys are investigated by using the first-principles exact muffin-tin orbital method in combination with coherent-potential approximation. It is shown that Fe atom prefers to occupy the Mn and Ni sublattices even in Ga-deficient alloys; Co has strong tendency to occupy the Ni sublattice in all types of alloys; Cu atoms always occupy the sublattice of the host elements in deficiency. For most of the alloys with stable site occupations, both the electron density n and the shear modulus C' can be considered as predictors of the composition dependence of the martensitic transition temperature TM of the alloys. The physics underlying the composition-dependent C' are discussed based on the calculated density of states. [ABSTRACT FROM AUTHOR]