Solid Solutions RE(16)Rh(11-x)Z(x) (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd, In, Sn, Sb, Pb, Bi) - Centrosymmetric n = 2 Variants of Parthé's Homologous Series A(5n+6)B(3n+5)

Tappe, F.,Schappacher, F.M.,Langer, T.,Schellenberg, I.,Pöttgen, R.,

Abstract

Several samples of solid solutions RE 16Rh 11-xZx (RE = La, Ce, Pr, Nd, Sm; Z = Ga, Zn, Cd, In, Sn, Sb, Pb, Bi) were synthesized by high-frequency melting of the elements in sealed tantalum ampoules. The samples were characterized by powder X-ray diffraction, and the structures of eight compounds were refined on the basis of single-crystal X-ray diffractometer data. The compounds crystallize with a centrosymmetric variant (space group P4/mbm) of the Ca 16Sb 11 type (P42 1m). The relation between both structure types is discussed on the basis of a group-subgroup scheme. Only for La 16Rh 8Sn 3 we observed full rhodium-tin ordering. The striking structural motif is a chain of face-sharing square prisms (filled with tin) and anti-prisms (filled with rhodium). The La 16Rh 8Sn 3 structure is closely related to the structure types W 5Si 3, Ca 16Sb 11, Y 3Rh 2, Sm 26Co 11Ga 6, Pu 31Pt 20, and Yb 36Sn 23 and is the centrosymmetric n = 2 member of Parthé's A 5n+6B 3n+5 series. 119Sn Mössbauer spectra resolved the two crystallographically independent tin sites of La 16Rh 8Sn 3, while a Pr 16Rh 9Sb 2 sample shows only a singlet in its 121Sb Mössbauer spectrum. © 2012 Verlag der Zeitschrift für Naturforschung.