Wang, W;
Fortes, AD;
Dobson, DP;
Howard, CM;
Bowles, J;
Hughes, NJ;
Wood, IG;
(2018)
Investigation of high-pressure planetary ices by cryo-recovery. II. High-pressure apparatus, examples and a new high-pressure phase of MgSO₄·5H₂O.
Journal of Applied Crystallography
, 51
(3)
pp. 692-705.
10.1107/S1600576718003977.
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Abstract
An apparatus is described for the compression of samples to ∼2 GPa at temperatures from 80 to 300 K, rapid chilling to 80 K whilst under load and subsequent recovery into liquid nitrogen after the load is released. In this way, a variety of quenchable high-pressure phases of many materials may be preserved for examination outside the high-pressure sample environment, with the principal benefit being the ability to obtain high-resolution powder diffraction data for phase identification and structure solution. The use of this apparatus, in combination with a newly developed cold-loadable low-temperature stage for X-ray powder diffraction (the PheniX-FL), is illustrated using ice VI (a high-pressure polymorph of ordinary water ice that is thermodynamically stable only above ∼0.6 GPa) as an example. A second example using synthetic epsomite (MgSO₄·7H₂O) reveals that, at ∼1.6 GPa and 293 K, it undergoes incongruent melting to form MgSO₄·5H₂O plus brine, contributing to a long-standing debate on the nature of the high-pressure behaviour of this and similar highly hydrated materials. The crystal structure of this new high-pressure polymorph of MgSO₄·5H₂O has been determined at 85 K in space group Pna2₁ from the X-ray powder diffraction pattern of a sample recovered into liquid nitrogen and is found to differ from that of the known ambient-pressure phase of MgSO₄·5H₂O (pentahydrite, space group [P {\overline 1}]), consisting of corner-sharing MgO₆—SO₄ ion pairs rather than infinite corner-sharing chains.
| Type: | Article |
|---|---|
| Title: | Investigation of high-pressure planetary ices by cryo-recovery. II. High-pressure apparatus, examples and a new high-pressure phase of MgSO₄·5H₂O |
| Location: | United States |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1107/S1600576718003977 |
| Publisher version: | https://doi.org/10.1107/S1600576718003977 |
| Language: | English |
| Additional information: | © 2018 Wang et al. This is an open access article distributed under the terms the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). |
| Keywords: | planetary ices, high pressure, cryo-recovery, epsomite, magnesium sulfate pentahydrate |
| UCL classification: | UCL 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/10050874 |
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