@article{discovery1468469, note = {This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.}, journal = {Acta Crystallographica Section E}, title = {Crystal structures of spinel-type Na2MoO4 and Na2WO4 revisited using neutron powder diffraction}, month = {June}, volume = {71}, pages = {592--596}, number = {Pt 6}, year = {2015}, issn = {2056-9890}, keywords = {neutron powder diffraction, sodium molybdate, sodium tungstate}, author = {Fortes, AD}, abstract = {Time-of-flight neutron powder diffraction data have been collected from Na2MoO4 and Na2WO4 to a resolution of sin ({\ensuremath{\theta}})/{\ensuremath{\lambda}} = 1.25 {\AA}(-1), which is substanti-ally better than the previous analyses using Mo K{\ensuremath{\alpha}} X-rays, providing roughly triple the number of measured reflections with respect to the previous studies [Okada et al. (1974 ?). Acta Cryst. B30, 1872-1873; Bramnik \& Ehrenberg (2004 ?). Z. Anorg. Allg. Chem. 630, 1336-1341]. The unit-cell parameters are in excellent agreement with literature data [Swanson et al. (1962 ?). NBS Monograph No. 25, sect. 1, pp. 46-47] and the structural parameters for the molybdate agree very well with those of Bramnik \& Ehrenberg (2004 ?). However, the tungstate structure refinement of Okada et al. (1974 ?) stands apart as being conspicuously inaccurate, giving significantly longer W-O distances, 1.819 (8) {\AA}, and shorter Na-O distances, 2.378 (8) {\AA}, than are reported here or in other simple tungstates. As such, this work represents an order-of-magnitude improvement in precision for sodium molybdate and an equally substantial improvement in both accuracy and precision for sodium tungstate. Both compounds adopt the spinel structure type. The Na(+) ions have site symmetry .-3m and are in octa-hedral coordination while the transition metal atoms have site symmetry -43m and are in tetra-hedral coordination.}, url = {http://dx.doi.org/10.1107/S2056989015008774} }