Preparation, crystal structure, physical properties, and electronic band structure of TlTaS3

TlTaS3 was prepared by applying a sequence of two melting processes with mixtures of Tl2S, Ta, and S having different molar metal to sulphur ratios. TlTaS3 crystallises in space group Puma with a = 9.228(3) Angstrom, b = 3.5030(6) Angstrom, c = 14.209(3) Angstrom, V = 459.3(2) Angstrom(3), Z = 4. The structure is closely related to the NH4CdCl3-type. Characteristic features of the structure are chains of edge-sharing [Ta(+5)S4S2/2](2) double octahedra running along [010]. These columns are linked by Tl+ ions. The Tl+ ion is surrounded by eight S2- anions to form a distorted bi-capped trigonal prism. The Tl+ ions are shifted from the centre of the trigonal prism toward one of the rectangular faces. This is discussed in context with other isostructural compounds. TlTaS3 is a semiconductor. The electronic structure is discussed on the base of band structure calculations performed within the framework of density functional theory.