Publication details
Reinvestigation of the crystal structure of kasolite, Pb[(UO2)(SiO4)](H2O), an important alteration product of uraninite, UO2+x
| Authors | |
|---|---|
| Year of publication | 2013 |
| Type | Article in Periodical |
| Magazine / Source | JOURNAL OF NUCLEAR MATERIALS |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1016/j.jnucmat.2010.11.064 |
| Field | Geology and mineralogy |
| Keywords | uranyl silicate; kasolite; crystal structure; spent nuclear fuel |
| Description | The crystal structure of kasolite, Pb[(UO2)(SiO4)](H2O), Z = 4, monoclinic, with a = 6.7050(3), b = 6.9257(2), c = 13.2857(5) angstrom, beta = 105.064(4)degrees, V = 595.74(3) angstrom(3), the space group P2(1)/c, has been solved by charge-flipping method and refined by the full-matrix least-squares techniques to an agreement factor (R-obs) of 2.2% and, a goodness-of-fit (GOF) of 1.26 using 1243 unique observed diffraction maxima (I-obs > 3 sigma(I)) collected with MoK alpha X-radiation and a 4 K CCD area detector. The crystal structure of kasolite contains 1 unique U6+ position that is part of a nearly linear uranyl ion (UO2)(2+), coordinated in the equatorial plane by five 0 ligands, forming pentagonal bipyramid. The uranyl pentagonal bipyramids share edges to form chains parallel to [0 1 0]. The additional edge of uranyl polyhedra is shared by silicate tetrahedra to form sheets parallel to (1 0 0). There is one unique position of Pb2+ in the interlayer. O ligands and 1 (H2O) non-transformer group coordinate Pb2+ exhibiting [2 + 6] coordination. A network of H-bonds provides an additional linkage of an interlayer to the sheets besides Pb-O bonds. Chemical composition of the studied crystals, obtained by the electron microprobe, is reported and is in agreement with the crystal structure refinement. (C) 2010 Elsevier B.V. All rights reserved. |