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Title: Identification of NpO 2+x in the binary Np-O system

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Journal Article: Publisher's Accepted Manuscript
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Journal of Nuclear Materials
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Journal Volume: 490; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-04 15:32:41; Journal ID: ISSN 0022-3115
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Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., and Shuh, David K. Identification of NpO 2+x in the binary Np-O system. Netherlands: N. p., 2017. Web. doi:10.1016/j.jnucmat.2017.04.019.
Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., & Shuh, David K. Identification of NpO 2+x in the binary Np-O system. Netherlands. doi:10.1016/j.jnucmat.2017.04.019.
Tayal, Akhil, Conradson, Steven D., Baldinozzi, Gianguido, Namdeo, Sonu, Roberts, Kevin E., Allen, Patrick G., and Shuh, David K. Sat . "Identification of NpO 2+x in the binary Np-O system". Netherlands. doi:10.1016/j.jnucmat.2017.04.019.
title = {Identification of NpO 2+x in the binary Np-O system},
author = {Tayal, Akhil and Conradson, Steven D. and Baldinozzi, Gianguido and Namdeo, Sonu and Roberts, Kevin E. and Allen, Patrick G. and Shuh, David K.},
abstractNote = {},
doi = {10.1016/j.jnucmat.2017.04.019},
journal = {Journal of Nuclear Materials},
number = C,
volume = 490,
place = {Netherlands},
year = {Sat Jul 01 00:00:00 EDT 2017},
month = {Sat Jul 01 00:00:00 EDT 2017}

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Publisher's Version of Record at 10.1016/j.jnucmat.2017.04.019

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  • The crystal structure has been determined for a new Np(V) mixed-ligand coordination compound Np(V), Cs/sub 4/(NpO/sub 2/)/sub 3/Cl/sub 6/(NO/sub 3/)H/sub 2/O; the crystals are orthorhombic, lattice parameters a = 1.960 (5), b = 1.326 (4), c = 0.854 (2) nm, space group Cmc2/sub 1/, Z = 4, rho/sub calc/ = 4.91 g/cm/sup 3/. The structure has been determined by the heavy-atom method from three-dimensional photographic x-ray data and refined by full-matrix least squares in the isotropic-anisotropic approximation to R = 0.104. The structure consists of ((NpO/sub 2/)/sub 2/Cl/sub 4/NpO/sub 2/Cl/sub 2/(NO/sub 3/)H/sub 2/O)/sub n//sup 4n-/ anion layers parallel to themore » (010) planes, between which there are double layers of cesium cations. The polymeric anion contains two crystallochemically nonequivalent neptunium atoms having pentagonal coordination around the Np(1)O/sub 2//sup +/ and Np(2)O/sub 2//sup +/ oxocations. This structure is an example of reliable evidence for direct interaction between Np(V) complexes involving the oxygen atoms in neptunoyl groups. The (Np(1)O/sub 2/Cl/sub 4/O) bipyramids are linked via common Cl-Cl edges into polymeric strips, which are linked by bipyramidal (Np(2)O/sub 2/Cl/sub 2/(NO/sub 3/)H/sub 2/O) complexes into polymeric layers via common oxygen vertices belonging to Np(2)O/sub 2//sup +/. The Np(1)O/sub 2//sup +/ dioxocation is virtually linear and symmetrical, with Np(1)-O distances of 0.180(3) and 0.179 (3) nm, while < O-Np(1)-O=178 (2)/sup 0/. The dioxocation of the other type Np(2)O/sub 2/ is symmetrical (2(Np - O) = 0.185 (4) nm) but is not linear (< O-Np(2)-O=173 (3)/sup 0/). Other structure details are discussed together with the nature the nitrate ion.« less
  • The reaction of NpO{sub 2} with SeO{sub 2} in the presence of CsCl at 180 {sup o}C results in the formation of Np(NpO{sub 2}){sub 2}(SeO{sub 3}){sub 3} (1). The structure of 1 consists of three crystallographically unique Np centers with three different coordination environments in two different oxidation states. Np(1) is found in a neptunyl(V), ONpO{sup +}, unit that is further ligated in the equatorial plane by three chelating SeO{sub 3}{sup 2-} anions to create a hexagonal bipyramidal NpO{sub 8} unit. A second neptunyl(V) cation also occurs for Np(2); it is bound by four bridging selenite anions and by themore » oxo atom from the Np(1) neptunyl cation to form a pentagonal bipyramidal, NpO{sub 7}, unit. The third neptunium center, Np(3), which contains Np(IV), is found in a distorted NpO{sub 8} dodecahedron. Np(3) is bound by five bridging selenite anions and by three neptunyl units via cation-cation interactions. The NpO{sub 7} pentagonal bipyramids and NpO{sub 8} hexagonal bipyramids share both corners and edges. Both of these polyhedra share corners via cation-cation interactions with the NpO{sub 8} dodecahedra creating a three-dimensional structure with small channels that house the stereochemically active lone pair of electrons on the selenite anions. Magnetic susceptibility data follow Curie-Weiss behavior over the entire temperature range measured (5 {<=} T {<=} 320 K). The effective moment, {mu}{sub eff} = 2.28 {mu}{sub B}, which represents an average over the three crystallographically inequivalent Np atoms, is within the expected range of values. There is no evidence of long-range ordering of the Np moments at temperatures down to 5 K, consistent with the negligible Weiss constant determined from fitting the susceptibility data. Crystallographic data: 1, orthorhombic, space group Pbca, a = 10.6216(5), b = 11.9695(6), and c = 17.8084(8) {angstrom} and Z = 8 (T = 193 K).« less
  • The systems CeO/sub 2/--Ce/sub 2/O/sub 3/--WO/sub 3/ and Ce/sub 2/O/sub 3/--WO/sub 3/--W are studied at high temperature. Six compounds were found as stable phases in the system Ce/sub 2/O/sub 3/--WO/sub 3/. The compound 3Ce/sub 2/O/sub 3/ . WO/sub 3/ has a fluoritelike cubic structure of a/sub 0/ = 11.040 A and forms solid solutions with constituent oxides or CeO/sub 2/. The compound 3Ce/sub 2/O/sub 3/ . 2WO/sub 3/, which seems to be isostructural with 3 La/sub 2/O/sub 3/ . 2WO/sub 3/, is stable only in the temperature range, 1545 approximately 1730/sup 0/C. The compound Ce/sub 2/O/sub 3/ . WO/sub 3/,more » which has a monoclinic structure, transforms reversibly at 1360/sup 0/C to a tetragonal structure with the cell parameters a/sub 0/ = 5.469 A, c/sub 0/ = 8.790 A. The compound Ce/sub 2/O/sub 3/ . 2WO/sub 3/ identified to be monoclinic, also has a reversible transformation at 1105/sup 0/C. Its high-temperature phase has a cubic cell with the cell parameter a = 7.046 A. As is well known, Ce/sub 2/O/sub 3/ . 3WO/sub 3/ appeared to have similar high-temperature behavior to La/sub 2/O/sub 3/ . 3WO/sub 3/. The compound 2Ce/sub 2/O/sub 3/ . 9WO/sub 3/, whose structure could not be analyzed, melts congruently at 1026/sup 0/C. 7 tables, 3 figures, 29 references.« less