Site preference and vibrational properties of R3T4+xAl12−x (R=Y, Ce, Gd, U, Th; T=Fe, Ru)

The crystal structures and phase stability of the ternary alloys R3T4+xAl12−x (R=Y, Ce, Gd, U, Th; T=Fe, Ru) have been investigated using the interatomic potentials obtained by the lattice inversion method. These compounds crystallize in the hexagonal Gd3Ru4Al12-type structure and the calculated lattice constants correspond well with the experiments. Among the four different kinds of Al sites in the structure, the most preferential sites for Fe atoms or Ru atoms are 6h sites. The properties related to lattice vibration, such as the phonon density of states (DOS) and Debye temperature of R3Fe4Al12, have been evaluated. A qualitative analysis is carried out with the relevant potentials for the vibrational modes, which makes it possible to predict some thermodynamic properties.