THE STRUCTURE OF AURICHALCITE, (CU,ZN)(5)(OH)(6)(CO3)(2), DETERMINED FROM A MICROCRYSTAL

Aurichalcite occurs as a natural mineral and also as a synthetically produced intermediate in the preparation of important copper/zinc oxide catalysts for a variety of industrial hydrogenation processes. Synchrotron radiation has allowed structure determination by single-crystal methods using a flake of material 5 mu m thick. The crystals are monoclinic and twinned. As in the related mineral hydrozincite, Zn-5(OH)(6)(CO3)(2) [Ghose (1964). Acta Cryst. 17, 1051-1057], there are double layers of close-packed O atoms, with metal atoms in octahedral holes, as well as tetrahedrally coordinated metal atoms. In contrast to hydrozincite, there are also five-coordinate metal atoms. Alternate layers are linked only by hydrogen bonds and the metal coordination octahedra show strong tetragonal distortion. The tetrahedral sites are probably occupied by zinc, the other sites by zinc and copper.