IN4TE3 AND IN4SE3 - REDETERMINATION OF CR YSTAL-STRUCTURE, PRESSURE-DEPENDENT BEHAVIOR AND A NOTE ON THE NONEXISTENCE OF IN4S3

The X-ray crystal structures of the two black, isotypic, mixed valent solids In4Te3 (a = 15.619(1) Angstrom, b = 12.749(1) Angstrom, c = 4.4 348(3) Angstrom, space group Pnnm, Z = 4) and In4Se3 (a = 15.296(1) An gstrom, b = 12.308(1) Angstrom, c = 4.0806(5) Angstrom), were redeterm ined using single crystals isolated from homogeneous, microcrystalline samples. X-ray powder investigations in the composition range In4Se3- xSx (0 < x < 3) revealed heterogeneous samples for x > 1, indicating t he non-existence of ''In4S3'' under these conditions. High pressure X- ray experiments with In,Te, (powder and single crystals) and In4Se3 (p owder) showed pronounced anisotropies of the compressibilities for the normal pressure modifications, which can be correlated to the structu re and bonding situations in both compounds. At 4.1 GPa In4Te3 decompo ses to In + 3InTe, the latter one crystallizing in a rocksalt structur e and incorporating excess Indium in the sense In1+xTe. At 16.0 GPa th e mixture In + 3InTe undergoes a second phase transition. In4Se3 trans forms to a new high pressure phase of unknown structure at 8.8 GPa.