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 p roduced intermediate in the preparation of important copper/zinc oxide catalysts for a variety of industrial hydrogenation processes. Synchr otron radiation has allowed structure determination by single-crystal methods using a flake of material 5 mu m thick. The crystals are monoc linic and twinned. As in the related mineral hydrozincite, Zn-5(OH)(6) (CO3)(2) [Ghose (1964). Acta Cryst. 17, 1051-1057], there are double l ayers of close-packed O atoms, with metal atoms in octahedral holes, a s well as tetrahedrally coordinated metal atoms. In contrast to hydroz incite, there are also five-coordinate metal atoms. Alternate layers a re 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.