TY - JOUR

T1 - Crystallographic mechanism of the elastic behaviour of synthetic bütschliite K2Ca(CO3)2 on compression to 20 GPa

AU - Likhacheva, Anna Yu

AU - Romanenko, Alexandr V.

AU - Rashchenko, Sergey V.

AU - Miloš, Sofija

AU - Lotti, Paolo

AU - Miletich, Ronald

AU - Shatskiy, Anton

N1 - AL, AR, SR and AS received financial support from RFBR (grant # 21-55-14001); AS was also supported by the state assignment of GEOKHI RAS; SM and RM received financial support from FWF (grant # I 5046-N). We appreciate profound and constructive criticisms of anonymous reviewers, which helped to improve the manuscript. This work is financially supported by the joint RFBR-FWF grant project (# 21-55-14001 and I 5046-N) and performed on state assignment of IGM SB RAS (No. 122041400176-0). We acknowledge the European Synchrotron Radiation Facility (ESRF) for the provision of synchrotron beamtime (proposal ES-1061) and we would like to thank Prof. Michael Hanfland and Dr. Davide Comboni for assistance and support in using beamline ID015b. The Elettra Sincrotrone Trieste is also acknowledged for provision of beamtime (exp. 20220403). We are grateful to Dr. Boby Joseph for assistance in using beamline Xpress.

PY - 2024/9

Y1 - 2024/9

N2 - Bütschliite, K2Ca(CO3)2, occurring as inclusions in mantle minerals, is regarded as one of the key phases to understand phase relationships of dense potassium carbonates and thus to evaluate their potential role within the Earth’s deep carbon cycle. Accordingly, the high-pressure behavior of synthetic bütschliite has been investigated by in-situ single-crystal X-ray diffraction under isothermal compression up to 20 GPa at T = 298 K. The compression mechanism before and after the trigonal-to-monoclinic (R-3m to C2/m) phase transition at ∼6 GPa, found previously, is characterized in terms of the evolution of the cation polyhedra and carbonate groups. On this basis, the modulation of the axial compression is interpreted, and the contribution of the cation polyhedra into the bulk compression is estimated. The refined compressibility of the monoclinic phase (K0 = 44(2) GPa) fits to the trend of the carbonate bulk modulus versus average non-carbon cation radius. The analysis of the obtained and literature structural data suggests the distortion of a large cation polyhedron to be an effective tool to strengthen the carbonate structure at high pressure. On the other hand, the observed symmetrization of the cation polyhedra in trigonal bütschliite is apparently a crucial factor of its stabilization at high pressure upon the temperature rise observed previously. The structural crystallography provided in this study supports the enhanced stability of trigonal bütschliite at high P, T conditions and its significance of being considered as a constituent of the inclusions in deep minerals.

AB - Bütschliite, K2Ca(CO3)2, occurring as inclusions in mantle minerals, is regarded as one of the key phases to understand phase relationships of dense potassium carbonates and thus to evaluate their potential role within the Earth’s deep carbon cycle. Accordingly, the high-pressure behavior of synthetic bütschliite has been investigated by in-situ single-crystal X-ray diffraction under isothermal compression up to 20 GPa at T = 298 K. The compression mechanism before and after the trigonal-to-monoclinic (R-3m to C2/m) phase transition at ∼6 GPa, found previously, is characterized in terms of the evolution of the cation polyhedra and carbonate groups. On this basis, the modulation of the axial compression is interpreted, and the contribution of the cation polyhedra into the bulk compression is estimated. The refined compressibility of the monoclinic phase (K0 = 44(2) GPa) fits to the trend of the carbonate bulk modulus versus average non-carbon cation radius. The analysis of the obtained and literature structural data suggests the distortion of a large cation polyhedron to be an effective tool to strengthen the carbonate structure at high pressure. On the other hand, the observed symmetrization of the cation polyhedra in trigonal bütschliite is apparently a crucial factor of its stabilization at high pressure upon the temperature rise observed previously. The structural crystallography provided in this study supports the enhanced stability of trigonal bütschliite at high P, T conditions and its significance of being considered as a constituent of the inclusions in deep minerals.

KW - Alkali carbonate

KW - Compressibility

KW - Crystal structure

KW - High pressure

KW - Single-crystal X-ray diffraction

KW - Synthetic bütschliite

UR - https://www.scopus.com/record/display.uri?eid=2-s2.0-85199968658&origin=inward&txGid=5115802e6aa1c71ad576603a33f159f1

UR - https://www.mendeley.com/catalogue/25c686db-0473-3605-9531-d59006845a5e/

U2 - 10.1007/s00269-024-01291-8

DO - 10.1007/s00269-024-01291-8

M3 - Article

VL - 51

JO - Physics and Chemistry of Minerals

JF - Physics and Chemistry of Minerals

SN - 0342-1791

IS - 3

M1 - 29

ER -