UCL  IRIS
Institutional Research Information Service
UCL Logo
Please report any queries concerning the funding data grouped in the sections named "Externally Awarded" or "Internally Disbursed" (shown on the profile page) to your Research Finance Administrator. Your can find your Research Finance Administrator at https://www.ucl.ac.uk/finance/research/rs-contacts.php by entering your department
Please report any queries concerning the student data shown on the profile page to:

Email: portico-services@ucl.ac.uk

Help Desk: http://www.ucl.ac.uk/ras/portico/helpdesk
Publication Detail
Isothermal equation of state and high-pressure phase transitions of synthetic meridianiite (MgSO4·11D2O) determined by neutron powder diffraction and quasielastic neutron spectroscopy
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Article
  • Authors:
    Fortes AD, Fernandez-Alonso F, Tucker M, Wood IG
  • Publication date:
    31/01/2017
  • Pagination:
    33, 46
  • Journal:
    Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials
  • Volume:
    73
  • Issue:
    1
  • Status:
    Published
  • Print ISSN:
    2052-5192
Abstract
© International Union of Crystallography, 2017.We have collected neutron powder diffraction data from MgSO4·11D2O (the deuterated analogue of meridianiite), a highly hydrated sulfate salt that is thought to be a candidate rock-forming mineral in some icy satellites of the outer solar system. Our measurements, made using the PEARL/HiPr and OSIRIS instruments at the ISIS neutron spallation source, covered the range 0.1 < P < 800 MPa and 150 < T < 280 K. The refined unit-cell volumes as a function of P and T are parameterized in the form of a Murnaghan integrated linear equation of state having a zero-pressure volume V0 = 706.23 (8) Å3, zero-pressure bulk modulus K0 = 19.9 (4) GPa and its first pressure derivative, K′ = 9 (1). The structure's compressibility is highly anisotropic, as expected, with the three principal directions of the unit-strain tensor having compressibilities of 9.6 × 10-3, 3.4 × 10-2 and 3.4 × 10-3 GPa-1, the most compressible direction being perpendicular to the long axis of a discrete hexadecameric water cluster, (D2O)16. At high pressure we observed two different phase transitions. First, warming of MgSO4·11D2O at 545 MPa resulted in a change in the diffraction pattern at 275 K consistent with partial (peritectic) melting; quasielastic neutron spectra collected simultaneously evince the onset of the reorientational motion of D2O molecules with characteristic time-scales of 20-30 ps, longer than those found in bulk liquid water at the same temperature and commensurate with the lifetime of solvent-separated ion pairs in aqueous MgSO4. Second, at ∼ 0.9 GPa, 240 K, MgSO4·11D2O decomposed into high-pressure water ice phase VI and MgSO4·9D2O, a recently discovered phase that has hitherto only been formed at ambient pressure by quenching small droplets of MgSO4(aq) in liquid nitrogen. The fate of the high-pressure enneahydrate on further compression and warming is not clear from the neutron diffraction data, but its occurrence indicates that it may also be a rock-forming mineral in the deep mantles of large icy satellites.
Publication data is maintained in RPS. Visit https://rps.ucl.ac.uk
 More search options
UCL Researchers
Author
Dept of Earth Sciences
Author
Dept of Earth Sciences
University College London - Gower Street - London - WC1E 6BT Tel:+44 (0)20 7679 2000

© UCL 1999–2011

Search by