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Structure of magnesium selenate enneahydrate, MgSeO 4 ·9H 2 O, from 5 to 250 K using neutron time‐of‐flight Laue diffraction
Author(s) -
Fortes A. Dominic,
Alfè Dario,
Hernández Eduardo R.,
Gutmann Matthias J.
Publication year - 2015
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520615006824
Subject(s) - neutron diffraction , selenate , magnesium , time of flight , diffraction , x ray crystallography , materials science , crystallography , chemistry , analytical chemistry (journal) , physics , selenium , crystal structure , optics , metallurgy , chromatography
The complete structure of MgSeO 4 ·9H 2 O has been refined from neutron single‐crystal diffraction data obtained at 5, 100, 175 and 250 K. It is monoclinic, space group P 2 1 / c , Z = 4, with unit‐cell parameters a = 7.222 (2), b = 10.484 (3), c = 17.327 (4) Å, β = 109.57 (2)°, and V = 1236.1 (6) Å 3 [ρ calc = 1770 (1) kg m −3 ] at 5 K. The structure consists of isolated [Mg(H 2 O) 6 ] 2+ octahedra, [SeO 4 ] 2− tetrahedra and three interstitial lattice water molecules, all on sites of symmetry 1. The positions of the H atoms agree well with those inferred on the basis of geometrical considerations in the prior X‐ray powder diffraction structure determination: no evidence of orientational disorder of the water molecules is apparent in the temperature range studied. Six of the nine water molecules are hydrogen bonded to one another to form a unique centrosymmetric dodecamer, (H 2 O) 12 . Raman spectra have been acquired in the range 170–4000 cm −1 at 259 and 78 K; ab initio calculations, using density functional theory, have been carried out in order to aid in the analysis of the Raman spectrum as well as providing additional insights into the geometry and thermodynamics of the hydrogen bonds. Complementary information concerning the thermal expansion, crystal morphology and the solubility are also presented.