Structure and phase transition of the Se-rich variety of antimonpearceite, [(Ag,Cu)6(Sb,As)2(S,Se)7][Ag9Cu(S,Se)2Se2].

摘要: The crystal structure of a Se-rich antimonpearceite has been solved and refined by means X-ray diffraction data collected at temperatures above (room temperature) below (120 K) an ionic conductivity-induced phase transition. Both arrangements consist the stacking [(Ag,Cu)(6)(Sb,As)(2)(S,Se)(7)](2-) A (A') [Ag(9)Cu(S,Se)(2)Se(2)](2+) B (B') module layers in which Sb forms isolated SbS(3) pyramids typically occurring sulfosalts; copper links two S atoms linear coordination, silver occupies sites with coordination ranging from quasi-linear to almost tetrahedral. In ionic-conducting form, room temperature, d(10) ions are found layer along two-dimensional diffusion paths their electron densities described combination Gram-Charlier development atomic displacement factors split-atom model. resembles that pearceite, except for presence both specific (Se) mixed (S, Se) sites. low-temperature ;ordered' 120 K located well defined S-Se is then similar 222-pearceite but major differences, specifically its cell metric, symmetry local arrangement layer.