Posnjakite: 2 ∞[Cu4(OH)6(H2O)O] octahedral sheets in its structure

Abstract

Abstract The crystal structure of posnjakite (space group Pa, a = 10.578, b = 6.345, c = 7.863 Å, β = 117.98°) was determined by direct methods and refined to a final R value of 0.05. The structure is characterized by corrugated sheets of distorted copper octahedra with crystal chemical formula 2 ∞Cu4(OH)6(H2O)O]. Sulphate groups are connected to one side of the octahedral sheet by corner sharing. The resultant composite octahedraltetrahedral layers are connected to each other by hydrogen bonds. The crystal chemical formula of posnjakite is Cu4(SO4)(OH)6 · H2O with two such units in the unit cell. The relations of posnjakite with other copper sulphate hydrates are noted and discussed.