Synthesis and structure of two phases with both extended and point defects: Mn1 − xBi2 + yS4andMn1 − xBi2 + ySe4

Abstract

We report the structures of Mn 1 − x Bi 2 + y S 4 (0 ⩽ x ⩽ 0.3; y = 0.667 x) and Mn 1 − x Bi 2 + y Se 4 (0.1 ⩽ x ⩽ 0.14; y = 0.667 x). Both compounds are defect structures of the HgBi 2S 4 structure type. In the case of Mn 0.7Bi 2.2S 4 we report a single crystal structure. The cell parameters are a = 12.869(2) A ̊ , b = 3.9546(6) A ̊ , c = 14.771(2) A ̊ , β = 116.690(9) o and the space group is C2/ m. Final refinement gave the values R/R w = 3.3 3.7 % . This crystal was grown in an alkali halide flux. The reported compounds belongs to the family of chemically twinned face-centered cubic (f.c.c.) structures. Unlike most members of this family, they exhibit both extended defects and point defects.