Physics and Chemistry of Minerals

, Volume 35, Issue 4, pp 207–221

The crystal structure and thermal expansion tensor of MgSO4–11D2O(meridianiite) determined by neutron powder diffraction

Original Paper

DOI: 10.1007/s00269-008-0214-x

Cite this article as:
Fortes, A.D., Wood, I.G. & Knight, K.S. Phys Chem Minerals (2008) 35: 207. doi:10.1007/s00269-008-0214-x

Abstract

We have collected high-resolution neutron powder diffraction patterns from MgSO4·11D2O over the temperature range 4.2–250 K. The crystal is triclinic, space-group \( \text{P} \bar{1} \) (Z = 2) with a = 6.72746(6) Å, b = 6.78141(6) Å, c = 17.31803(13) Å, α = 88.2062(6)°, β = 89.4473(8)°, γ = 62.6075(5)°, and V = 701.140(6) Å3 at 4.2 K, and a = 6.75081(3) Å, b = 6.81463(3) Å, c = 17.29241(6) Å, α = 88.1183(3)°, β = 89.4808(3)°, γ = 62.6891(3)°, and V = 706.450(3) Å3 at 250 K. Structures were refined to wRp = 3.99 and 2.84% at 4.2 and 250 K, respectively. The temperature dependence of the lattice parameters over the intervening range have been fitted with a modified Einstein oscillator model which was used to obtain the coefficients of the thermal expansion tensor. The volume thermal expansion, αV, is considerably smaller than ice Ih at all temperatures, and smaller even than MgSO4·7D2O (although ∂αV/∂T is very similar for both sulfates); MgSO4·11D2O exhibits negative αV below 55 K (compared to 70 K in D2O ice Ih and 20 K in MgSO4·7D2O) The relationship between the magnitude and orientation of the principal axes of the expansion tensor and the main structural elements are discussed.

Supplementary material

269_2008_214_MOESM1_ESM.doc (328 kb)
Supplementary tables (DOC 327 kb)
269_2008_214_MOESM2_ESM.doc (652 kb)
(CIF 651 kb)
269_2008_214_MOESM3_ESM.doc (625 kb)
(CIF 625 kb)

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.Center for Planetary Sciences, Department of Earth SciencesUniversity College LondonLondonUK
  2. 2.ISIS FacilityRutherford Appleton LaboratoryDidcotUK
  3. 3.The Natural History MuseumLondonUK

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