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Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction.

Fortes, AD; (2015) Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction. Acta Crystallographica Section E: Structure Reports Online , 71 (7) pp. 799-806. 10.1107/S2056989015011354. Green open access

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Abstract

Time-of-flight neutron powder diffraction data have been measured from ~90 mol. % deuterated isotopologues of Na₂MoO₄·2H₂O and Na₂WO₄·2H₂O at 295 K to a resolution of sin(θ)/λ = 0.77 / Å. The use of neutrons has allowed refinement of structural parameters with a precision that varies by a factor of two from the heaviest to the lightest atoms; this contrasts with the X-ray refinements where precision may be > 20x poorer for O in the presence of atoms such as Mo and W. The accuracy and precision of interatomic distances and angles are in excellent agreement with recent X-ray single-crystal structure refinements whilst also completing our view of the hydrogen-bond geometry to the same degree of statistical certainty. The two structures are isotypic, space-group Pbca, with all atoms occupying general positions, being comprised of edge- and corner-sharing NaO₅ and NaO₆ polyhedra that form layers parallel with (010), interleaved with planes of XO₄ (X = Mo, W) tetrahedral that are linked by chains of water molecules along [100] and [001]. The complete structure is identical with the previously described molybdate [Capitelli et al. (2006) Asian J. Chem. 18, 2856-2860] but shows that the purported three-centred interaction involving one of the water molecules in the tungstate [Farrugia (2007) Acta Cryst. E 63, i142] is in fact an ordinary two-centred 'linear' hydrogen bond.

Type: Article
Title: Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction.
Open access status: An open access version is available from UCL Discovery
DOI: 10.1107/S2056989015011354
Publisher version: http://dx.doi.org/10.1107/S2056989015011354
Additional information: Copyright © International Union of Crystallography. This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Keywords: Neutron powder diffraction; sodium molybdate dihydrate; sodium tungstate dihydrate.
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1469205
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