Crystal structure of Cu2Se

Abstract

The crystal structures of the low-temperature (space group C2/c, Pearson symbol mS144, a = 7.1379(4) Å, b = 12.3823(7) Å, с = 27.3904(9) Å, β = 94.308º, RI = 0.0765) and high-temperature (space group Fm-3m, Pearson symbol cF12, a = 5.859(1) Å, R1 = 0.0391) modifications of Cu2Se were determined by means of X-ray powder and single crystal diffraction. The basic features of the two modifications are similar. The Se atoms are stacked in a close-packed arrangement with the layers in the sequence ABC. The Cu atoms are distributed over all tetrahedral interstices. The positions of Cu are completely ordered in the low- temperature modification, whereas they are disordered in the high-temperature modification.