Single-crystal structure determination of two new ternary bismuthides: Rh6Mn5Bi18 and RhMnBi3

Abstract

A study of the ternary Rh–Mn–Bi phase diagram revealed the existence of two new ternary bismuthides, viz. hexarhodium pentamanganese octadecabismuthide (Rh6Mn5Bi18) and rhodium manganese tribismuthide (RhMnBi3). Their crystal structures represent new structure types. Rh6Mn5Bi18, with a Wyckoff sequence a f2 g2 i5, crystallizes in the tetragonal system (space group P42/mnm; Pearson symbol tP58), and RhMnBi3, with a Wyckoff sequence a c g i q, crystallizes in the orthorhombic system (Cmmm; oS20). In the Rh6Mn5Bi18 structure, the transition metal atoms are linked into ribbon-like structural units aligned along the [001] direction, whereas planar sheets are formed in RhMnBi3. In both crystal structures, the units formed by the transition metal atoms are enveloped by Bi atoms, which themselves form a loosely bound network. The linkage results in a layer structure for RhMnBi3, while in the case of Rh6Mn5Bi18, a three-dimensional network is formed; the latter, however, contains several areas where Bi...Bi distances suggest van der Waals interactions. Both phases under discussion have analogous structural motifs.