Informace o publikaci
The (3+3) commensurately modulated structure of the uranyl silicate mineral swamboite-(Nd), Nd-0.333[(UO2)(SiO3OH)](H2O)(2.41)
| Autoři | |
|---|---|
| Rok publikování | 2018 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | ZEITSCHRIFT FUR KRISTALLOGRAPHIE-CRYSTALLINE MATERIALS |
| Fakulta / Pracoviště MU | |
| Citace | |
| Doi | http://dx.doi.org/10.1515/zkri-2017-2119 |
| Klíčová slova | commensurate; crystal structure; modulation; swamboite; uranyl silicate |
| Popis | The uranyl mineral swamboite has been redefined to swamboite-(Nd) and its structure has been solved and refined as a commensurate structure in six-dimensional superspace. The structure is monoclinic, superspace group P2(1)/m(a1, b1, g1) 00(-a1, b1, g1) 00 (a2,0,g2)0s, cell parameters a = 6.6560(3), b = 6.9881(5), c = 8.8059(6), c = 11.3361(16) angstrom, beta = 102.591(5)degrees, modulation wave-vectors q(1) = 1/3 1/3 0; q(2) = - 1/3 1/3 0; q(3) = 1/2 0 1/2. The structure was refined from 8717 reflections to a final R = 0.0610. The model includes modulation both of atomic positions and displacement parameters, as well as occupancy waves. The structure is based upon uranyl-silicate sheets of uranophane topology alternating with an inter-layer of partly occupied Nd3+ sites and H2O molecules. The strong (3 + 3) dimensional modulation of the structure originates from the distribution of the Nd-dominated sites and further accommodation of the suitable geometry within the sheets and charge distribution within the structure. The separation distances between the corres-ponding occupied Nd sites are rationals of the super-cell vectors corresponding to the modulation vectors of the structure. The case of swamboite-(Nd) is the first example of a modulated structure within the oxysalts of U6+. |