Atomistic simulation of site preference, Curie temperature, and lattice vibration of Nd₂Co_{7 - x}Fe_x

The effects of Fe substitution for Co on the structural stability and the site preference of intermetallics Nd_2Co_7 - xFe_x with a hexagonal Ce_2Ni_7-type structure are studied by using a series of interatomic pair potentials. In Nd_2Co_7 - xFe_x, Fe atoms are substituted for Co atoms with a strong preference for the 6h sites and the order of site preference is 6h, 4e, 4f, 2a, and 12k. Calculated lattice parameters are found to be consistent with the reported results in the literature. The variation behaviour of the Curie temperature of Nd_2Co_7 - xFe_x is explained qualitatively by the exchange interaction model. The properties related to lattice vibration, such as phonon density of states and Debye temperature, are first evaluated for the Nd_2Co_7 - xFe_x compounds.