Crystal structures of the R3Ag1−δTSe7 (R = La–Nd, Sm, Gd–Dy, δ = 0–0.30; T = Ge, Si) compounds

The crystal structures of the R3Ag1−δGeSe7 (R = La–Nd, Sm, Gd–Dy, δ = 0.06–0.28) and R3Ag1−δSiSe7 (R = La–Nd, Sm, Gd–Dy, δ = 0–0.30) compounds were determined by means of X-ray single crystal diffraction (space group P63): a = 1.0806(1) nm, c = 0.6111(1) nm, R1 = 0.0280 for La3Ag0.94GeSe7; a = 1.0711(1) nm, c = 0.60719(5) nm, R1 = 0.0126 for Ce3Ag0.89GeSe7; a = 1.0619(1) nm, c = 0.6070(1) nm, R1 = 0.0387 for Pr3Ag0.89GeSe7; a = 1.0621(1) nm, c = 0.60531(6) nm, R1 = 0.0166 for Nd3Ag0.87GeSe7; a = 1.0479(1) nm, c = 0.60258(8) nm, R1 = 0.0165 for Sm3Ag0.81GeSe7; a = 1.0428(1) nm, c = 0.60321(5) nm, R1 = 0.0187 for Gd3Ag0.85GeSe7; a = 1.0364(1) nm, c = 0.60399(6) nm, R1 = 0.0274 for Tb3Ag0.82GeSe7; a = 1.0271(1) nm, c = 0.6057(1) nm, R1 = 0.0202 for Dy3Ag0.72GeSe7; a = 1.0817(1) nm, c = 0.60640(4) nm, R1 = 0.0185 for La3AgSiSe7; a = 1.0731(1) nm, c = 0.6031(1) nm, R1 = 0.0200 for Ce3AgSiSe7; a = 1.0655(1) nm, c = 0.6005(1) nm, R1 = 0.0221 for Pr3AgSiSe7; a = 1.0602(1) nm, c = 0.5988(1) nm, R1 = 0.0177 for Nd3AgSiSe7; a = 1.0497(1) nm, c = 0.59466(6) nm, R1 = 0.0378 for Sm3Ag0.85SiSe7; a = 1.0433(1) nm, c = 0.59367(7) nm, R1 = 0.0206 for Gd3Ag0.81SiSe7; a = 1.0362(1) nm, c = 0.59296(5) nm, R1 = 0.0161 for Tb3Ag0.70SiSe7; a = 1.0332(1) nm, c = 0.59494(5) nm, R1 = 0.0115 for Dy3Ag0.72SiSe7. Gradual decrease of the silver amount has been observed in the series of chalcogenides. It was reported that the existence of two different positions of the silver atom implies Ag deficiency. Disordered position of the silver atom can be connected to ionic conductivity of R3AgTSe7 compounds.