Isothermal section of the Cu 2Se–HgSe–GeSe 2 system at 670 K and crystal structures of the compounds Cu 2HgGeSe 4 and HT-modification of Cu 2HgGeS 4

Abstract

The isothermal section of quasi-ternary Cu 2Se–HgSe–GeSe 2 system at 670 K was constructed. The crystal structures of the compounds Cu 2HgGeSe 4 (Cu 2FeSnS 4 structure type, space group I 4 ¯ 2 m , a = 0.57456(2) nm, c = 1.10834(4) nm, R I = 0.0468) and HT-modification of Cu 2HgGeS 4 (Cu 2CdGeS 4 structure type, space group Pmn2 1, a = 0.76882(3) nm, b = 0.65561(2) nm, c = 0.63144(3) nm, R I = 0.0835) were determined using X-ray powder diffraction. The Se atoms in the structure of the Cu 2HgGeSe 4 compound are stacked in a close-packed arrangement with layers in the sequence ABC. Half of the tetrahedral interstices are occupied by Cu, Hg and Ge atoms. At the same time the S atoms in the structure of the HT-modification of Cu 2HgGeS 4 are stacked in a close-packed arrangement with layers in the sequence AB. Half of the tetrahedral interstices are occupied by cations.