Revision of the crystal structure and chemical formula of haiweeite, Ca(UO2)2(Si5O12)(OH)2•6H2O

被引:17
作者
Plasil, Jakub [1 ]
Fejfarova, Karla [1 ]
Cejka, Jiri [2 ]
Dusek, Michal [1 ]
Skoda, Radek [3 ]
Sejkora, Jiri [2 ]
机构
[1] Inst Phys ASCR, Vvi, Prague 18221 8, Czech Republic
[2] Natl Museum, Dept Mineral & Petrol, CZ-19300 Prague 9, Czech Republic
[3] Masaryk Univ, Fac Sci, Inst Geol Sci, CZ-61137 Brno, Czech Republic
关键词
Haiweeite; uranyl silicate; sheets of polyhedra; crystal structure; X-ray diffraction; BOND-VALENCE PARAMETERS; URANYL SILICATE SHEET; URANIUM; WEEKSITE; MINERALS;
D O I
10.2138/am.2013.4284
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
The previously published crystal structure study suggested that haiweeite is orthorhombic, Cmcm, with a = 7.125(1), b = 17.937(2), c = 18.342(2) angstrom, and V = 2344.3(7) angstrom(3), and an ideal chemical formula Ca[(UO2)(2)Si5O12(OH)(2)]center dot 3H(2)O, with Z = 4. Using single-crystal X-ray diffraction and electron microprobe analysis we re-examined haiweeite from the Teofilo Otoni, Minas Gerais, Brazil. Our diffraction experiment provided weak reflections responsible for doubling of the b cell parameter (for the current space-group settings), leading finally to the choice of a different space group. Haiweeite is thus orthorhombic, the space group Pbcn, with the unit-cell parameters a = 18.3000(5), b = 14.2331(3), c = 17.9192(5) angstrom, V = 4667.3(2) angstrom(3), and an ideal formula Ca[(UO2)(2)(SiO3OH)(2)(Si3O6)].6H(2)O (6.25 H2O inferred from the thermal analysis; 7.50 H2O from the structure model), with Z= 8. The structure refinement yielded R-1 = 0.0512 for 2498 observed reflections [I-obs > 3 sigma(I)] and wR(2) = 0.1286 for all 6117 unique reflections. Structure solution confirmed by subsequent refinement provided a structure model with full occupancies for U, Si, and Ca atoms, contrasting to previous average structure model. Although the general topology of our structure resembles that reported previously, all Si and O sites in our structure are fully occupied, in contrast to the previous structure determination.
引用
收藏
页码:718 / 723
页数:6
相关论文
共 20 条
[1]   BOND-VALENCE PARAMETERS FOR SOLIDS [J].
BRESE, NE ;
OKEEFFE, M .
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, 1991, 47 :192-197
[2]   BOND-VALENCE PARAMETERS OBTAINED FROM A SYSTEMATIC ANALYSIS OF THE INORGANIC CRYSTAL-STRUCTURE DATABASE [J].
BROWN, ID ;
ALTERMATT, D .
ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE, 1985, 41 (AUG) :244-247
[3]   U6+ minerals and inorganic compounds:: Insights into an expanded structural hierarchy of crystal structures [J].
Burns, PC .
CANADIAN MINERALOGIST, 2005, 43 :1839-1894
[4]  
Burns PC, 1998, CAN MINERAL, V36, P1069
[5]  
Burns PC, 1997, CAN MINERAL, V35, P1551
[6]   A new uranyl silicate sheet in the structure of haiweeite and comparison to other uranyl silicates [J].
Burns, PC .
CANADIAN MINERALOGIST, 2001, 39 (04) :1153-1160
[7]   THE IMPORTANCE OF ACCURATE CRYSTAL-STRUCTURE DETERMINATION OF URANIUM MINERALS .2. SODDYITE (UO2)2(SIO4).2H2O [J].
DEMARTIN, F ;
GRAMACCIOLI, CM ;
PILATI, T .
ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS, 1992, 48 :1-4
[8]   Revision of the crystal structure and chemical formula of weeksite, K2(UO2)2(Si5O13)•4H2O [J].
Fejfarova, Karla ;
Plasil, Jakub ;
Yang, Hexiong ;
Cejka, Jiri ;
Dusek, Michal ;
Downs, Robert T. ;
Barkley, Madison C. ;
Skoda, Radek .
AMERICAN MINERALOGIST, 2012, 97 (04) :750-754
[9]   Reinvestigation of the crystal structure of kasolite, Pb[(UO2)(SiO4)](H2O), an important alteration product of uraninite, UO2+x [J].
Fejfarova, Karla ;
Dusek, Michal ;
Plasil, Jakub ;
Cejka, Jiri ;
Sejkora, Jiri ;
Skoda, Radek .
JOURNAL OF NUCLEAR MATERIALS, 2013, 434 (1-3) :461-467