Theoretical study of structure and lattice vibrations of R3Co11−xFexB4 (R=Nd, Gd)

The intermetallics R3Co11−xFexB4 (R=Nd, Gd) have been studied to ascertain the effect of partial replacement of Co by Fe on their phase stability and site preference. Calculation is based on a series of interatomic pair potentials related to the rare earth, B and transition metals, which are obtained by a strict lattice inversion method. The site preference of the quaternary element Fe is found to be the 3g sites. The calculated lattice constants agree with a report in the literature. Furthermore, the total and partial phonon densities of states are evaluated for the R3Co11B4 compounds with the hexagonal Ce3Co11B4-type structure. The analysis of the inverted potentials explains qualitatively the contributions of different atoms to the vibrational modes.