Abstract: | In the crystal structures of the minerals edoylerite, deanesmithite, and wattersite and in the structures of the compounds HgCrO4, Hg3O2CrO4 (analog of the mineral schuetteite), and Pb2HgO2CrO4, there are atomic groups or fragments linked by relatively strong (covalent) bonds. The anion fragments represented by CrO4 tetrahedra are condensed into pairs and chains, in which adjacent tetrahedra are related by symmetry centers. The cation fragments form various patterns from zigzag ribbons of [Hg4S4] rings to ribbons and frameworks with [Hg6O2] r-octahedra, [Hg2CrO] and [Pb2HgO] triangles, and [Hg6Cr2O4] (stella quadrangula) groups. The symmetry of the fragments and their assemblies is analyzed. Analysis of the reference crystal-forming planes has revealed cation sublattices (close to the F-cubic sublattice in two cases), determining the typical features of the structures.Original Russian Text Copyright © 2004 by S. V. Borisov, S. A. Magarill, and N. V. PervukhinaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 471–479, May–June, 2004. |