Natural and synthetic compounds with krošhnkite-type chains. An update
- Author(s)
- Michel Fleck, Uwe Kolitsch
- Abstract
The crystal structures of five new triclinic double salt dihydrates have been determined from single-crystal X-ray diffraction data. The following four compounds all contain krošhnkite-[Na2Cu(SO4)2 ž 2 H2O]-type tetrahedral-octahedral chains: the three isotypic synthetic compounds K2Mg(CrO4)2 ž 2 H2O (a = 5.674(1), b = 6.462(1), c = 7.517(2) A°, a = 110.38(3), ß = 95.24(3), ? = 109.86(3)°, V = 236.0(1) A°3, R(F) = 0.036, space group P1¯, no. 2, Z = 1), K2Mg(MoO4)2 ž 2 H2O (a = 5.884(1), b = 6.491(1), c = 7.700(1) A°, a = 111.67(2), ß = 96.59(2), ? = 108.62(2)°, V= 249.8(1) A°3, R(F) = 0.019, space group P1¯, no. 2, Z = 1) and K2Mn(SeO4)2 ž 2 H2O (a = 5.674(1), b = 6.608(1), c = 7.523(2) A°, a = 110.31(3), ß = 95.69(3), ? = 108.35(3)°, V = 244.10(9) A°3, R(F) = 0.024, space group P1¯, no. 2, Z = 1), and the mineral messelite Ca2(Fe2+,Mn2+,Mg)(PO4) 2 ž 2 H2O (a = 5.480(1), b = 5.759(1), c = 6.569(1) A°, a = 90.18(3), ß = 102.62(3), ? = 108.45(3)°, V = 191.3(1) A°3, R(F) = 0.022, space group P1¯, no. 2, Z = 1). The fifth compound, the synthetic dichromate K2Zn(Cr2O7)2 ž 2 H2O (a = 6.794(1), b = 7.735(2), c = 7.834(2) A°, a = 88.97(3), ß = 80.90(3), ? = 64.57(3)°, V = 366.5(2) A°3, R(F) = 0.036, space group P1¯, no. 2, Z = I) is closely related to the krošhnkite-group; it contains Cr2O7 groups assuming the same bridging role that XO4 groups have in krošhnkite-type oxysalts. The atomic arrangements of the title compounds are described and structural relations with other krošhnkite-type and -like compounds are discussed. In addition, related yavapaiite-type sheet structures of AM'(XO4)2 compounds are briefly reviewed, including the rod group symmetry of the underlying krošhnkite-chain building unit. Twelve different space groups have been found for these sheet structures. The previously reported space group symmetries for a-NH4Fe(CrO4)2 (P21) and CsTa(PO4)2 (P1¯) are obviously incorrect and should be revised to P21/n and C2/m, respectively.
- Organisation(s)
- Department of Mineralogy and Crystallography
- Journal
- Zeitschrift für Kristallographie : international journal for structural, physical, and chemical aspects of crystalline materials
- Volume
- 218
- Pages
- 553-567
- No. of pages
- 15
- ISSN
- 0044-2968
- Publication date
- 2003
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 1051 Geology, Mineralogy
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/0ef175a0-77f0-4e6e-96fa-6da49cb14f7e