The system Cu 3 AsS 4 –Cu 3 SbS 4 and investigations on normal tetrahedral structures

✍ Scribed by Pfitzner, Arno; Bernert, Thomas

• Book ID: 120373557
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2004
• Tongue: English
• Weight: 188 KB
• Volume: 219
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.219.1.20.25398

✦ Synopsis

Abstract

In order to develop a novel model to predict if a so called normal tetrahedral compound crystallizes in a__wurtzite__- or__sphalerite__superstructure type, the system Cu~3~AsS~4~–Cu~3~SbS~4~was reinvestigated. A solid solution series was prepared and the mixed crystals were characterized by powder X-ray techniques. The crystal structures of Cu~3~As~0.330~Sb~0.670~S~4~, Cu~3~As~0.736~Sb~0.264~S~4~, and Cu~3~AsS~4~were refined from single crystal X-ray data. The refinements converged to__R__= 0.0209,__wR__2 = 0.0484 (Cu~3~As~0.330~Sb~0.670~S~4~, 201 unique reflections, 15 parameters),R= 0.0235,wR__2 = 0.0596 (Cu~3~As~0.736~Sb~0.264~S~4~, 218 reflections, 15 parameters), and__R= 0.0241,__wR__2 = 0.0669 (Cu~3~AsS~4~, 721 reflections, 45 parameters).__Z__is 2 for all compounds. The volumes of the tetrahedra [MS~4~] were calculated for the investigated compounds. In addition, the corresponding data were calculated for further solids from literature data. The volumes of the tetrahedra are used to separate compounds with a__sphalerite__type anion arrangement from compounds with hexagonal packed anions. A closer inspection of the tetrahedra volumes reveals a greater variation for one given material in the case of__wurtzite__type superstructures than for__sphalerite__type superstructures. A critical difference in the tetrahedra volumes is derived from these data.