HIGH-PRESSURE SYNTHESIS AND CRYSTAL-STRUCTURE OF AG2GA6TE10

Ag//2Ga//6Te//1//0 was synthesized from a mixture of AgGaTe//2 and AgGa//5Te//8 at 2. 0 GPa and 900 degree C in a modified Belt high pressure apparatus. The black lath-like crystals are monoclinic (space group, C2) with a equals 14. 33 A, b equals 14. 308 A, c equals 10. 127 A, beta equals 90. 2 degree and Z equals 4. The arrangement of the tellurium sublattice is nearly identical with the beta -manganese structure. Gallium atoms occupy a number of the tetrahedral holes in the structure, forming GaTe//4 tetrahedra and Ga//2Te//6 double tetrahedra. The mobile silver ions are distributed over incompletely filled positions with irregular coordination.