Product evolution in the Np(IV) fluorophosphate system
- Department of Chemistry and Biochemistry and the E. C. Leach Nuclear Science Center, Auburn University, Auburn, AL 36849 (United States)
- Department of Chemistry, University of South Alabama, Mobile, AL 36688 (United States)
- Chemical Sciences Division, Transuranium Research Laboratory, Oak Ridge National Laboratory, MS 6375, Oak Ridge, TE 37831 (United States)
The reaction of {sup 237}NpO{sub 2} with Cs{sub 2}CO{sub 3}, Ga{sub 2}O{sub 3}, H{sub 3}PO{sub 4}, and HF under mild hydrothermal conditions leads to the formation of NpFPO{sub 4} after 4 days at 180 deg. C. Heating at 180 deg. C for an additional 6 days leads to the crystallization of Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4} and NpF{sub 4}. The Ga{sub 2}O{sub 3} forms a GaPO{sub 4} matrix in which crystals of NpFPO{sub 4}, Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4}, and NpF{sub 4} grow. Single crystal X-ray data reveal that the structure of NpFPO{sub 4} consists of Np(IV) centers bound by both fluoride and phosphate to yield [NpF{sub 2}O{sub 6}] distorted dodecahedra. These are linked by corner-sharing with fluoride and both corner- and edge-sharing with phosphate to yield a dense, three-dimensional network. The structure of Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4} is complex and contains both distorted dodecahedral [NpO{sub 2}F{sub 6}] and tricapped trigonal prismatic [NpO{sub 2}F{sub 7}] environments around Np(IV) that are linked with each other through corner- and edge-sharing, and with the phosphate groups to create a three-dimensional structure. There are small channels extending down the a-axis in Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4}. Crystallographic data: NpFPO{sub 4}, orthorhombic, space group Pnma, a=8.598(2), b=6.964(1), c=6.337(1) A, Z=4, V=379.44(13) A{sup 3}, R(F)=3.53% for 40 parameters and 465 reflections with I>2{sigma}(I) (T=193 K); Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4}, monoclinic, space group P2{sub 1}/c, a=8.8727(4), b=16.2778(7), c=7.8009(4) A, {beta}=112.656(1), Z=4, V=1039.73(8) A{sup 3}, R(F)=2.27% for 146 parameters and 2465 reflections with I>2{sigma}(I) (T=193 K). - Graphical abstract: Two Np(IV) fluorophosphates, NpFPO{sub 4} and Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4}, have been prepared as single crystals under hydrothermal conditions. NpFPO{sub 4} crystallizes first, then reacts to yield Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4} and finally yields NpF{sub 4}. Single crystal X-ray structures of NpFPO{sub 4} and Cs{sub 2}Np{sub 2}F{sub 7}PO{sub 4} show three-dimensional frameworks containing Np(IV) in both eight- and nine-coordinate environments.
- OSTI ID:
- 21015620
- Journal Information:
- Journal of Solid State Chemistry, Vol. 180, Issue 1; Other Information: DOI: 10.1016/j.jssc.2006.09.019; PII: S0022-4596(06)00533-0; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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