BIGAIN2S6 - SYNTHESIS, STRUCTURE, AND PROPERTIES

The novel compound BiGaIn2S6 was obtained in the quaternary system Bi- Ga-In-S. BiGaIn2S6 forms red transparent platelets and exhibits a rang e of homogeneity between BiGa1In2S6 and BiGa0.8In2.2S6. The compound i s a semiconductor with E-g(opt.) = 1.9 eV. - BiGaIn2S6 crystallizes mo noclinically forming a new structure type (a= 1112.0 pm, b = 380.6 pm, c = 1228.0 pm, beta = 116.30 degrees, Z = 2, space group P2(1)/m, no. 11). The S atoms form strongly corrugated 2D fragments of the (hc)(2) sphere packing type. The In atoms occupy octahedral holes ((d) over b ar(In-S) = 262 pm) and the Ga atoms tetrahedral holes ((d) over bar(Ga -S) = 234 pm) inside the 2D-layers. The Bi atoms on the top of trigona l BiS3 pyramids ((d) over bar(Bi-S) = 265 pm) are at the periphery of the layers and have four additional S ligands from the neigbouring lay er at much larger distances ((d) over bar(Bi-S) = 319 pm). - The bondi ng of a Bi-III sulfide is analyzed for the first time by the Electron Localization Function (ELF).