A REDETERMINATION OF THE CRYSTAL-STRUCTURE OF THE (III)A-POLYTYPIC FORM OF DIINDIUM ZINC TETRASULFIDE, ZNIN2S4

The crystal structure of the layered semiconductor (III)a-ZnIn2S4 was reported by Lappe et al. (1962) to be in space group R3m. This description implies an ordered distribution of Zn and In over the tetrahedrally coordinated positions. A redetermination of the structure using both single-crystal and powder X-ray data showed that space group R3mBAR is the correct one for (III)a-ZnIn2S4. The structure was refined to R = 0.049, R(w) = 0.037 for 573 absorption-corrected reflections. ZnIn2S4 (R3mBAR, hexagonal axes a = 3.8674(3) angstrom, c = 37.007(5) angstrom, c/a = 9.569, Z = 3) crystallizes with a nearly close-packed layered structure (sequence of the S layers A B C A\C A B C\B C A B) with In(oct) in octahedral coordination (In(oct)-S = 6 x 2.620(l) angstrom) and M(tet) (= 0.5 ln + 0.5 Zn) in tetrahedral coordination (M(tet) - S = 1 x 2.468(3) and 3 x 2.378(l) angstrom). The relations of (III)a-ZnIn2S4 to other polytypic forms of this compound are discussed.