Die Kristallstruktur von synthetischem Parapierrotit, TlSb5S8*

Abstract

The crystal structure of synthetic parapierrotite, TlSb₅S₈, has been determined. The crystal is monoclinic with space group C[unk] – Pn. Four formula units are contained in a until cell of dimensions a = 8.098(5), b = 19.415(12), c = 9.059(6)Å, β = 91.96(8)°. The structure was determined by Patterson methods and refined to a final R-value of 0.07 for 4489 observed reflections. The structure consists of corrugated infinite Sb₅S₈-double layers parallel (101) which exhibit a deformed NaCl-type structure between the n-glide planes. Between parallel layers the shortest Sb – S distance is 3.37 Å. Along the n-glide planes the NaCl-type structure is interrupted, and this is the place where the Tl atoms fit between the layers. The two independent Tl atoms are coordinated by eight respectively nine S atoms. The coordination polyhedra around the Tl atoms are trigonal prisms with two or three additional S atoms located near the side faces. The Sb-atoms are in an octahedral environement, but clearly show three, four or five nearest neighbours. The mean Tl^VIII – S and Tl^IX – S distances are 3.31 and 3.39 A. The mean Sb^III – S, Sb^IV – S, and Sb^V – S distances are 2.49, 2.62, and 2.66 Å, respectively.