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First-principles calculations of high-pressure iron-bearing monoclinic dolomite and single-cation carbonates with internally consistent Hubbard U

Solomatova, Natalia V. and Asimow, Paul D. (2018) First-principles calculations of high-pressure iron-bearing monoclinic dolomite and single-cation carbonates with internally consistent Hubbard U. Physics and Chemistry of Minerals, 45 (3). pp. 293-302. ISSN 0342-1791. https://resolver.caltech.edu/CaltechAUTHORS:20180425-125649087

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Abstract

It has been proposed that iron has a significant effect on the relative stability of carbonate phases at high pressures, possibly even stabilizing double-cation carbonates (e.g., dolomite) with respect to single-cation carbonates (e.g., magnesite, aragonite and siderite). X-ray diffraction experiments have shown that dolomite transforms at ~35 GPa to a high-pressure polymorph that is stable to decomposition; however, there has been disagreement on the structure of the high-pressure phase (Mao et al. in Geophys Res Lett 38, 2011. doi: 10.1029/2011GL049519; Merlini et al. in Proc Natl Acad Sci 109:13509–13514, 2012. doi: 10.1073/pnas.1201336109). Ab initio calculations interfaced with an evolutionary structure prediction algorithm demonstrated that a C2/c polymorph of pure CaMg(CO_3)_2 dolomite is more stable than previously reported structures (Solomatova and Asimow in Am Mineral 102:210–215, 2017, doi: 10.2138/am-2017-5830). In this study, we calculate the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory to accurately characterize the electronic structure of Fe. When calculated with a constant U of 4 eV, the spin transition pressure of (Mg,Fe)CO_3 agrees well with experiments, whereas an internally consistent U overestimates the spin transition pressure by ~50 GPa. However, whether we use constant or internally consistent U values, a higher iron concentration increases the stability field of dolomite C2/c with respect to single-cation carbonate assemblages, but iron-free dolomite is not stable with respect to single-cation carbonates at any pressure. Thus, high-pressure polymorphs of Fe-bearing dolomite could in fact represent an important reservoir for carbon storage within oxidized sections of Earth’s mantle.


Item Type:Article
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URLURL TypeDescription
https://doi.org/10.1007/s00269-017-0918-xDOIArticle
https://link.springer.com/article/10.1007%2Fs00269-017-0918-xPublisherArticle
https://rdcu.be/MAPLPublisherFree ReadCube access
ORCID:
AuthorORCID
Solomatova, Natalia V.0000-0002-2331-3427
Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2017 Springer-Verlag GmbH Germany. Received: 16 May 2017; Accepted: 17 August 2017; Published online: 28 August 2017. We thank K. Jarolimek, H. Hsu and H.J. Kulik for discussions. We are thankful to N. Near-Ansari for assistance with compiling relevant software and managing libraries on FRAM, the high-performance computing cluster at Caltech. This work is supported by the U.S. National Science Foundation through award EAR-1551433.
Funders:
Funding AgencyGrant Number
NSFEAR-1551433
Subject Keywords:Dolomite; Ankerite; Siderite; Carbonates; High pressure; Lower mantle
Issue or Number:3
Record Number:CaltechAUTHORS:20180425-125649087
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20180425-125649087
Official Citation:Solomatova, N.V. & Asimow, P.D. Phys Chem Minerals (2018) 45: 293. https://doi.org/10.1007/s00269-017-0918-x
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:86034
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Apr 2018 21:28
Last Modified:03 Oct 2019 19:38

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