TY - JOUR
T1 - Ultrahigh-pressure disordered eight-coordinated phase of Mg2GeO4
T2 - Analogue for super-Earth mantles
AU - Dutta, Rajkrishna
AU - Tracy, Sally June
AU - Cohen, R. E.
AU - Miozzi, Francesca
AU - Luo, Kai
AU - Yang, Jing
AU - Burnley, Pamela C.
AU - Smith, Dean
AU - Meng, Yue
AU - Chariton, Stella
AU - Prakapenka, Vitali B.
AU - Duffy, Thomas S.
N1 - Publisher Copyright:
© 2022 National Academy of Sciences. All rights reserved.
PY - 2022/2/22
Y1 - 2022/2/22
N2 - Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2SiO4, 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 I42 - d structure indistinguishable from I43 - 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.
AB - Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2SiO4, 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 I42 - d structure indistinguishable from I43 - 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.
KW - Order-disorder transition
KW - Post-postperovskite
KW - Super-Earth mineralogy
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U2 - 10.1073/pnas.2114424119
DO - 10.1073/pnas.2114424119
M3 - Article
C2 - 35165195
AN - SCOPUS:85124680394
SN - 0027-8424
VL - 119
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 8
M1 - e2114424119
ER -