Copper Bismuth Chalcogenide Halogenides with Extensively Disordered and Mobile Copper(I) Cations

Abstract

A new family of quaternary phases with the general sum formula Cu 3+δ Bi 5-δ Se 8-2δ X 2+2δ (X = Cl, Br) was discovered by slow cooling of high temperature melts. Cu 3.58(1) Bi 4.42(1) Se 6.84(2) Cl 3.16(2) (δ = 0.58) and Cu 4.52(1) Bi 3.48(1) Se 4.96(2) Br 5.04(2) (δ = 1.52) crystallize isostructural in the orthorhombic space group type Pnnm with a = 1332.3(1)/1340.2(3) pm, b = 1683.7(2)/1717.2(1) pm, and c = 406.2(1)/407.1(2) pm. The new structure type resembles in some aspects the hollandite as well as the pavonite type. A framework of faceand edge-sharing anion polyhedra around Bi 3+ cations hosts Cu + cations. The characteristic motif is an infinite band of polyhedra that has