摘要
The crystal structure of a compound with a nominal composition Ba 2 Fe 4 S 5 was determined from 432 observed structure amplitudes. The lattice constants are a = 4.016(2), Å, b = 9.616(4), Å, c = 6.514(4), Å, Pmmn, Z = 1. The structure consists of BaS 6 trigonal prisms that share triangular faces to form infinite columns parallel to a. Zig-zag chains of Fe are formed parallel to b by filling the tetrahedral interstices. The structure can also be viewed as an infinite two-dimensional plane of FeS 4 tetrahedra formed by the sharing of two edges of a face in the ±a directions and connecting by corner sharing in the ±b directions. The Ba are in the trigonal prismatic interstices. The apical sulfur atom shows an anomalously large temperature factor and has a 50% site occupancy. On the basis of full occupancy of that site the composition corresponds to BaFe 2 S 3 . This structure is closely related to the previously reported BaFe 2 S 3 and may be an averaged structure due to twinning of a polymorph of BaFe 2 S 3 . © 1982.