CRYSTAL-STRUCTURE OF CLINOATACAMITE, A NEW POLYMORPH OF CU-2(OH)(3)CL

The crystal structure of clinoatacamite, Cu-2(2+)(OH)(3)Cl, has been d etermined and refined to indices R = 5.2 and wR = 4.9%. The structure is monoclinic, space group P2(1)/n (14), with cell parameters a 6.144( 1), b 6.805(1), c 9.112(1) Angstrom, beta 99.55(3)degrees, V 375.7(2) Angstrom(3), and with Z = 4. The structure analysis was essential in d etermining the valence state of copper (Cu2+) and the number of (OH)(- ) anions in the formula. The structure consists of layers of partly oc cupied, edge-sharing octahedra of Jahn-Teller-distorted [Cu(OH)(4)Cl-2 ] octahedra parallel to (101). This layer is topologically the same as that in mica. Adjacent layers of octahedra are offset, such that vaca nt sites in one sheet align with occupied sites in the neighboring she et. Layers are linked by individual, slightly Jahn-Teller-distorted oc tahedra of composition [Cu(OH)(6)]. The structures of paratacamite and the other polymorphs of Cu-2(OH)(3)Cl, atacamite and botallakite, als o are layered, but they differ from the layering of clinoatacamite in topology, composition and cross-linkage.