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Published February 14, 2022 | Version v1
Journal article Open

Ultrahigh-pressure disordered eight-coordinated phase of Mg2GeO4: Analogue for super-Earth mantles

Creators

  • 1. Carnegie Institution for Science
  • 2. University of Nevada
  • 3. Argonne National Laboratory
  • 4. University of Chicago
  • 5. Princeton University

Description

Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2GeO4, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, Th3P4-type structure. DFT computations suggest partial Mg-Ge order, resulting in a tetragonal I 4 ¯ 2 d structure indistinguishable from I 4 ¯ 3 d Th3P4 in our experiments. If applicable to silicates, the formation of this highly coordinated and intrinsically disordered phase may have important implications for the interior mineralogy of large, rocky extrasolar planets.

Data availability

A sample input file for the DFT calculations performed in this work has been deposited in the Open Science Framework (DOI: https://doi.org/10.17605/OSF.IO/FM87E). All other data are included in the article and/or the SI Appendix.

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dutta-et-al-2022-ultrahigh-pressure-disordered-eight-coordinated-phase-of-mg2geo4-analogue-for-super-earth-mantles.pdf

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Additional details

Identifiers

DOI
10.1073/pnas.2114424119
Other
oai:uchicago.tind.io:10359

Funding

National Science Foundation
EAR-1836852
Carnegie Endowment
National Science Foundation
EAR-1634415
US Department of Energy
DE-FG02-94ER14466
US Department of Energy
DE-AC02-06CH11357

UChicago Information

Division(s)
Institutes & Centers
Center(s) or Institute(s)
Center for Advanced Radiation Sources