Study of the structure and lattice vibrations of Ce6Rh30Si19 and A6Pt30Si19 (A = Th, U)

We present an atomistic study on the phase stability, site preference and lattice constants of the rare earth or actinium intermetallics Ce6Rh30Si19 and A6Pt30Si19 (A = Th, U). The calculated preferential occupation site of one Si atom is found to be the 2b site in Ce6Rh30Si19 and A6Pt30Si19. The Si atom is located at the sites 2b with occupancy close to 50%. Our calculated lattice constants agree with a report in the literature. The total and partial phonon densities of states are evaluated first for these complicated defect structures. The analysis of the inverted potentials explains qualitatively the contributions of different atoms to the vibrational modes.