Ab initio studies of structural stability and magnetism in Ni3In -: art. no. 054440

To understand the structural stability and magnetism in the intermetallic compound Ni3In, we have performed total energy and electronic structure calculations for Ni3In as well as Ni3Al in the cubic L1(2), tetragonal D0(22), and hexagonal D0(19) structures. The highly accurate full-potential linearized augmented-plane-wave method has been used. The calculations are based on first-principles density-functional theory with generalized gradient approximation. The theoretical equilibrium lattice constants and bulk moduli of both the compounds are in good agreement with available experiments. Surprisingly, unlike Ni3Al and other related intermetallics, Ni3In in the nonmagnetic state is predicted to energetically favor the D0(22) structure rather than the L1(2) structure. However, the L1(2) and D0(19) structures are found to be magnetically unstable while the D0(22) structure is not. Ferromagnetism would make the L1(2) structure slightly lower in energy than the D0(22) structure by merely 7 meV/f.u. Therefore, the present theoretical work suggests that Ni3In at low temperatures is a weak ferromagnet and undergoes a structural and magnetic phase transformation as the temperature is raised to the room temperature. This picture would allow one to consistently interpret previous structural experiments and measured x-ray absorption spectra. Moreover, it is also predicted that unlike Ni3Al and other related intermetallics, there would be a pressure-induced structural phase transition from the L1(2) to D0(22) in Ni3In at low temperatures. It is hoped that these interesting findings would stimulate further experimental investigations such as temperature-dependent structural, specific-heat, and magnetization experiments on this nearly or weakly magnetic intermetallic compound.