Un nouveau matériau, Ag9GaSe6: Etude structurale de la phase α

Abstract α-Ag 9 GaSe 6 is cubic, space group F 4 3m , with a = 11.126(2) A and Z = 4. The diffraction pattern at 20°C using Mo K α radiation was collected with an automatic four-circle diffractometer. The structure was determined by beginning from the low-temperature structure (βAg 9 GaSe 6 ). An anisotropic full-matrix least-squares refinement was performed yielding a final R of 0.063 for the 103 reflections actually measured. The four Ga atoms and eight Se atoms are located on a 16( e ) position. All the GaSe bonds are 2.366(10) A. The Ag atoms are equally distributed on three sets of positions: two 48( h ) and one 96( i ). Among the 36 Ag atoms, 24 are bound to 3 Se atoms in an almost planar triangular arrangement (2.43(4)