THE CRYSTAL STRUCTURES OF X(NpO2)(PO4)(H2O)3 (X = K+, Na+, Rb+, NH4+) AND THEIR RELATIONSHIP TO THE AUTUNITE GROUP

T. Z Forbes; Peter C Burns

doi:10.2113/gscanmin.45.3.471

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THE CRYSTAL STRUCTURES OF X(NpO2)(PO4)(H2O)3 (X = K+, Na+, Rb+, NH4+) AND THEIR RELATIONSHIP TO THE AUTUNITE GROUP

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THE CRYSTAL STRUCTURES OF X(NpO2)(PO4)(H2O)3 (X = K+, Na+, Rb+, NH4+) AND THEIR RELATIONSHIP TO THE AUTUNITE GROUP

T. Z Forbes and Peter C Burns

Canadian mineralogist, Vol.45(3), pp.471-477

06/01/2007

DOI: 10.2113/gscanmin.45.3.471

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Abstract

Four Np6+ phosphates with compositions X(NpO2)(PO4)(H2O)3, X = K+, Na+, Rb+, NH4+, have been synthesized by mild hydrothermal methods, and their structures have been determined. Single-crystal X-ray-diffraction data were collected using MoKα radiation and an APEX CCD detector. The Np6+ structures containing K+, Na+, Rb+, and NH4+ (KP1, NaP1, RbP1, NH4P1) were refined to agreement indices R1 0.042, 0.051, 0.066, and 0.023 calculated for 831, 856, 798, and 857 unique observed reflections, respectively. KP1 crystallizes in space group P4/ncc, with a 6.9564(8), c 17.826(4) Å, V 862.6(2) Å3, Z = 4. NaP1 also is tetragonal, P4/ncc, with a 7.005(1), c 16.986(4) Å, V 833.6(3) Å3, Z = 4. RbP1 is tetragonal, P4/ncc, with a 7.031(4), c 17.87(2) Å, V 884(1) Å3, Z = 4. NH4P1 crystallizes in space group P4/ncc with a 6.9843(6), c 18.023(3) Å, V 879.2(2) Å3, Z = 4. Each of these structures contains sheets of composition [(NpO2)(PO4)]− consisting of Np6+ in square bipyramidal coordination and phosphate tetrahedra. These sheets are topologically identical to the well-known uranyl phosphate sheets of the autunite group. The monovalent cations and H2O group are located in the interlayer, where they balance the charge on the sheets and provide linkages between the sheets.

Details

Title: Subtitle: THE CRYSTAL STRUCTURES OF X(NpO2)(PO4)(H2O)3 (X = K+, Na+, Rb+, NH4+) AND THEIR RELATIONSHIP TO THE AUTUNITE GROUP
Creators: T. Z Forbes
Peter C Burns
Resource Type: Journal article
Publication Details: Canadian mineralogist, Vol.45(3), pp.471-477
DOI: 10.2113/gscanmin.45.3.471
ISSN: 0008-4476
eISSN: 1499-1276
Language: English
Date published: 06/01/2007
Academic Unit: Chemistry; Civil and Environmental Engineering; Core Research Facilities
Record Identifier: 9984216591802771

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