Physics and Chemistry of Minerals

, Volume 36, Issue 1, pp 29–46

The thermal expansion and crystal structure of mirabilite (Na2SO4·10D2O) from 4.2 to 300 K, determined by time-of-flight neutron powder diffraction

  • H. E. A. Brand
  • A. D. Fortes
  • I. G. Wood
  • K. S. Knight
  • L. Vočadlo
Original Paper

DOI: 10.1007/s00269-008-0256-0

Cite this article as:
Brand, H.E.A., Fortes, A.D., Wood, I.G. et al. Phys Chem Minerals (2009) 36: 29. doi:10.1007/s00269-008-0256-0

Abstract

We have collected high resolution neutron powder diffraction patterns from Na2SO4·10D2O over the temperature range 4.2–300 K following rapid quenching in liquid nitrogen, and over a series of slow warming and cooling cycles. The crystal is monoclinic, space-group P21/c (Z = 4) with a = 11.44214(4) Å, b = 10.34276(4) Å, c = 12.75486(6) Å, β = 107.847(1)°, and V = 1436.794(8) Å3 at 4.2 K (slowly cooled), and a = 11.51472(6) Å, b = 10.36495(6) Å, c = 12.84651(7) Å, β = 107.7543(1)°, V = 1460.20(1) Å3 at 300 K. Structures were refined to RP (Rietveld powder residual, \( R_{P} = {{\sum {\left| {I_{\text{obs}} - I_{\text{calc}} } \right|} } \mathord{\left/ {\vphantom {{\sum {\left| {I_{\text{obs}} - I_{\text{calc}} } \right|} } {\sum {I_{\text{obs}} } }}} \right. \kern-\nulldelimiterspace} {\sum {I_{\text{obs}} } }} \)) better than 2.5% at 4.2 K (quenched and slow cooled), 150 and 300 K. The sulfate disorder observed previously by Levy and Lisensky (Acta Cryst B34:3502–3510, 1978) was not present in our specimen, but we did observe changes with temperature in deuteron occupancies of the orientationally disordered water molecules coordinated to Na. The temperature dependence of the unit-cell volume from 4.2 to 300 K is well represented by a simple polynomial of the form V = − 4.143(1) × 10−7T3 + 0.00047(2) T2 − 0.027(2) T + 1437.0(1) Å3 (R2 = 99.98%). The coefficient of volume thermal expansion, αV, is positive above 40 K, and displays a similar magnitude and temperature dependence to αV in deuterated epsomite and meridianiite. The relationship between the magnitude and orientation of the principal axes of the thermal expansion tensor and the main structural elements are discussed; freezing in of deuteron disorder in the quenched specimen affects the thermal expansion, manifested most obviously as a change in the behaviour of the unit-cell parameter β.

Keywords

Mirabilite Sodium sulfate decahydrate Thermal expansion Neutron diffraction 

Supplementary material

269_2008_256_MOESM1_ESM.doc (464 kb)
Supplementary material (DOC 465 kb)

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  • H. E. A. Brand
    • 1
    • 2
  • A. D. Fortes
    • 1
    • 2
  • I. G. Wood
    • 1
    • 2
  • K. S. Knight
    • 3
    • 4
  • L. Vočadlo
    • 1
    • 2
  1. 1.Department of Earth ScienceUniversity College LondonLondonUK
  2. 2.Centre for Planetary SciencesUniversity College LondonLondonUK
  3. 3.ISIS FacilityRutherford Appleton LaboratoryOxfordshireUK
  4. 4.The Natural History MuseumLondonUK

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