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Pressure‐induced phase transition in MnCO 3 and its implications on the deep carbon cycle
Author(s) -
Boulard Eglantine,
Goncharov Alexander F.,
Blanchard Marc,
L. Mao Wendy
Publication year - 2015
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb011901
Subject(s) - rhodochrosite , triclinic crystal system , metastability , phase transition , diffraction , phase (matter) , synchrotron , materials science , crystallography , infrared spectroscopy , x ray crystallography , carbon fibers , chemistry , analytical chemistry (journal) , calcite , mineralogy , crystal structure , condensed matter physics , optics , physics , organic chemistry , chromatography , composite number , composite material
The high‐pressure behavior of manganese‐rich carbonate, rhodochrosite, has been characterized up to 62 GPa by synchrotron‐based midinfrared spectroscopy and X‐ray diffraction. Modifications in both the infrared spectra and the X‐ray diffraction patterns were observed above ~35 GPa, indicating the presence of a high‐pressure phase transition at these pressures. We found that rhodochrosite adopts a structure close to CaCO 3 ‐VI with a triclinic unit cell ( a = 2.87 Å, b = 4.83 Å, c = 5.49 Å, α = 99.86°, β = 94.95°, and γ = 90.95° at 62 GPa). Using first‐principles calculations based on density functional theory, we confirmed these observations and assigned modes in the new infrared signature of the high‐pressure phase. These results suggest that high‐pressure metastable phase of calcite may play an important role in carbon storage and transport in the deep Earth.