TY - JOUR

T1 - Stability of Ca2CO4- Pnma against the Main Mantle Minerals from Ab Initio Computations

AU - Sagatova, Dinara N.

AU - Shatskiy, Anton F.

AU - Gavryushkin, Pavel N.

AU - Sagatov, Nursultan E.

AU - Litasov, Konstantin D.

N1 - Funding Information: We thank the Information and Computing Center of the Novosibirsk State University for providing access to the cluster computational resources. The reported study was funded by the Russian Foundation for Basic Research, project no. 20-35-90043. A.F.S. and P.N.G. were supported by the state assignment of IGM SB RAS. K.D.L. was supported by the state assignment of IHPP RAS. Publisher Copyright: © 2021 American Chemical Society.

PY - 2021/7/15

Y1 - 2021/7/15

N2 - Recently, calcium orthocarbonate (Ca2CO4-Pnma) has been predicted to be stable under P-T conditions of the Earth's transition zone and the lower mantle. Here, we investigate its stability against the main mantle minerals in the pressure range of 20-100 GPa and temperatures of 1000-2000 K, based on the density functional theory within quasi-harmonic approximation. We found that Ca2CO4 appears in equilibrium with MgO (periclase) in the whole studied P-T range, while its coexistence with MgSiO3 (bridgmanite) is prohibited owing to the following reactions: Ca2CO4 + 2MgSiO3 → 2CaSiO3 + MgCO3 + MgO and Ca2CO4 + MgSiO3 + SiO2 → 2CaSiO3 + MgCO3. Our results revealed that Ca2CO4 can coexist with SiO2 up to 70-90 GPa at 500-2000 K where it reacts to produce carbon dioxide and Ca-perovskite, Ca2CO4 + 2SiO2 → 2CaSiO3 + CO2, typically observed as inclusions in ultradeep diamonds.

AB - Recently, calcium orthocarbonate (Ca2CO4-Pnma) has been predicted to be stable under P-T conditions of the Earth's transition zone and the lower mantle. Here, we investigate its stability against the main mantle minerals in the pressure range of 20-100 GPa and temperatures of 1000-2000 K, based on the density functional theory within quasi-harmonic approximation. We found that Ca2CO4 appears in equilibrium with MgO (periclase) in the whole studied P-T range, while its coexistence with MgSiO3 (bridgmanite) is prohibited owing to the following reactions: Ca2CO4 + 2MgSiO3 → 2CaSiO3 + MgCO3 + MgO and Ca2CO4 + MgSiO3 + SiO2 → 2CaSiO3 + MgCO3. Our results revealed that Ca2CO4 can coexist with SiO2 up to 70-90 GPa at 500-2000 K where it reacts to produce carbon dioxide and Ca-perovskite, Ca2CO4 + 2SiO2 → 2CaSiO3 + CO2, typically observed as inclusions in ultradeep diamonds.

KW - calcium orthocarbonate

KW - deep carbon cycle

KW - density functional theory

KW - lower mantle

KW - quasi-harmonic approximation

UR - http://www.scopus.com/inward/record.url?scp=85111139677&partnerID=8YFLogxK

U2 - 10.1021/acsearthspacechem.1c00065

DO - 10.1021/acsearthspacechem.1c00065

M3 - Article

AN - SCOPUS:85111139677

VL - 5

SP - 1709

EP - 1715

JO - ACS Earth and Space Chemistry

JF - ACS Earth and Space Chemistry

SN - 2472-3452

IS - 7

ER -