Structures of the rare-earth-platinum compounds R7Pt3, R2Pt, R5Pt3 and RPt

Structures of rare-earth-platinum compounds are identified. R7Pt3 compounds (R = La, Ce, Pr, Nd, Sm, Gd) crystallize with the Th7Fe3 structure type. PrPt and NdPt have a high-temperature modification which corresponds to the CrB type. R2Pt and R5Pt3 compounds crystallize with the Ni2Si and Mn5Si3 types, where R = Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y for both structure types. Atomic parameters were refined from single-crystal intensities collected on Gd2Pt. The coordination polyhedra of Ni2Si are compared with those of the Fe2P type. It is shown that a greatly idealized version of the Ni2Si type can be derived by periodic unit-cell twinning of the cubic-close-packed element structure. A survey of the known Rsub(x)Pt compounds (x>=1) is given. These compounds are compared with those occurring in the corresponding Ni and Pd systems. (Auth.)