Tl2S: re-determination of crystal structure and stereochemical discussion

摘要

The crystal structure of synthetic carlinite, Tl2S, was redetermined by single crystal and powder X-ray diffraction methods. The cell parameters obtained from Rietveld refinement are a = 12.150(2) Angstrom, c = 18.190(4) Angstrom, V = 2325.5(7) Angstrom(3). A single crystal data refinement proved Tl2S crystallizing in the trigonal space group R3 with M = 440.8 g mol(-1), Z = 27, R = 0.076, and wR = 0.145. The atomic arrangement found is that of a strongly deformed anti-Cd12 type, but the deformation is clearly different from that given by previous workers. In the five crystallographically different STl6 octahedra the S-Tl distances vary between 2.82 and 3.09 Angstrom, the Tl-Tl edges between 3.52 and 4.58 Angstrom. The common features of these octahedra are (i) each one with a definitely smaller vs larger Tl3 face in transposition, both faces parallel or sub-parallel (00.1), and (ii) each three shorter and longer S-TI distances to the atoms of the larger and smaller Tl3 faces, respectively. The TI-Tl contacts between different Tl2S sheets are on the average definitely shorter than the ones within the sheet and they can be smaller than the TI-Tl contacts in the small Tl-3 faces of the STl6 octahedra. The atomic arrangement indicates that the single electron pairs of the monovalent TI atoms are not arranged all parallel to the z-axis, as one would expect for Tl2S with an ideal anti-Cd12 structure. The surrounding of the S atoms resembles that of one-third of the Cl atoms in yellow InCl. The absorbance of Tl2S is very low at wave numbers approximately <9000cm(-1). (C) 2002 Elsevier Science (USA). [References: 32]