The crystal structure of kiddcreekite solved using micro X-ray diffraction and the EPCryst program

Abstract

Abundant kiddcreekite grains were identified in the Zijinshan Cu-Au epithermal deposit in Fujian Province, China. The mineral occurs as polycrystalline grains, 5–300 μm in size, associated with colusite, enargite, stannoidite, mawsonite, vinciennite, hemusite, tennantite and wolframite in a predominantly covellite ore. Based on electron microprobe analysis, the empirical formula of the kiddcreekite is Cu6.2Sn0.97W0.95S7.83, without significant Se or Te contents. The crystal structure of kiddcreekite was solved using the direct-space method (EPCryst) from laboratory micro X-ray diffraction (μXRD) data and refined by the Rietveld method. The R values of the final Rietveld refinement were Rp = 9.06%, Rwp = 8.31%, RB = 3.16 and RF = 2.17%. Kiddcreekite has a cubic structure, space group F4̄3m and lattice parameter a = 10.8178(3) Å (Z = 4, V = 1265.95(6) Å3). In the unit cell, W, Sn and Cu atoms occupy the 4a, 4c and 24f Wyckoff positions, respectively, and S atoms occupy two sets of 16e Wyckoff positions. The structure of kiddcreekite consists of stacked double MeS4 layers (giving a W–Sn–Cu tier and a Cu–vacancy tier) as in the sphalerite substructure. This study also demonstrates the possibility of using laboratory µXRD data coupled with the direct-space method to solve inorganic structures in cases where samples are too small for conventional powder and single-crystal diffraction.

Thermal Stability of the Crystal Structure and Electronic Properties of the High Power Factor Thermoelectric Colusite Cu26Cr2Ge6S32

“…Moreover, while some inorganic sulfide compounds are reported with either Mo 6+ − or W 6+ − cations in a tetrahedral environment of sulfur, the synthetic colusite Cu 26 Cr 2 Ge 6 S 32 is, to the best of our knowledge, the unique representative involving Cr 6+ cations in such kind of chemical environment. This was assumed to be related to the smaller ionic size and lower electronegativity of the Cr 6+ cation that should lead to lower thermal stability of Cr 6+ containing sulfides compared to those involving Mo 6+ , W 6+ , or V 5+ cations.…”