Acta Crystallographica Section B

Structural Science

Volume 65, Part 3 (June 2009)

research papers

Acta Cryst. (2009). B65, 334-341 [ doi:10.1107/S0108768109013901 ]

Structures of the pseudo-trigonal polymorphs of Cu₂(OH)₃Cl

T. Malcherek and J. Schlüter

Abstract: The crystal structure of Cu₂(OH)₃Cl has been determined using two natural samples with almost ideal stoichiometry. While one of the samples exhibits a twinned clinoatacamite structure, the other sample is characterized by the appearance of additional weak diffraction maxima at half integer positions of h and k. Structure refinement was carried out with the space group $P\bar 1$ . The relationship between the triclinic phase, clinoatacamite, paratacamite and the herbertsmithite structure is discussed in terms of symmetry as a function of Cu concentration.

Keywords: clinoatacamite; paratacamite; herbertsmithite; kagomè antiferromagnet.