REDETERMINATION OF THE CRYSTAL-STRUCTURE OF GAMMA-IN2SE3 BY TWIN CRYSTAL X-RAY-METHOD

The crystal structure of gamma-In2Se3 (P6(1) or P6(5), Z = 6, a = 712. 86(5), c = 1938.1(2) pm) was redetermined by X-ray structure determina tion methods confirming the results of Likforman et al. reported in 19 78 (8). The crystals (hexagonal pyramids and bipyramids, and small pla tes) obtained by chemical transport with iodine as transporting agent were multiple twins. The collected data of two twinned crystal specime ns were refined (final R1 = 0.0315 and 0.0559 for 1553 and 1602 indepe ndent reflections with I > 2 sigma(1), respectively). The structure is built up by In(1)Se-5 trigonal bipyramids and distorted In(2)Se-4 tet rahedra resulting in a distorted wurtzite-type-like arrangement. gamma -In2Se3 is the room-temperature polymorph of indium(III) selenide cont rary to some other reports in the literature, e.g., Julien et al. (198 5) (3). (C) 1996 Academic Press, Inc.