Ab initio investigation of the elastic properties of Ni3Fe.

Ab initio alloy theory, formulated within the exact muffin-tin orbitals method in combination with the coherent-potential approximation, is used to determine the elastic properties of Ni-Fe alloys with Fe:Ni ratio 1:3. The interplay between magnetic and chemical effects is investigated by computing the lattice parameters and the single- and polycrystal elastic moduli for different partially ordered structures in the ferro- and paramagnetic states. It is found that the influence of long-range chemical order on the bulk properties strongly depends on the magnetic state. The largest magnetic-order-induced changes are obtained for the chemically ordered L12 phase. The ferromagnetic L12 system possesses ~5.4% larger elastic Debye temperature than the paramagnetic L12 phase, which in turn has a similar ΘTD as the chemically disordered face-centered cubic phase in either the ferro- or paramagnetic state. It is concluded that magnetic ordering has a substantially larger impact on the bulk parameters of Ni3Fe than chemical ordering. The calculated trends are explained based on the electronic structure of nonmagnetic, ferromagnetic, and paramagnetic ordered and disordered phases. [ABSTRACT FROM AUTHOR]