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Open AccessArticle

High-Pressure Phase Diagrams of Na2CO3 and K2CO3

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Department of Geology and Geophysics, Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
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Sobolev Institute of Geology and Mineralogy, Siberian Branch of the Russian Academy of Science, prosp. acad. Koptyuga 3, Novosibirsk 630090, Russia
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GFZ German Research Center for Geosciences, Section 4.3, Telegrafenberg, 14473 Potsdam, Germany
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Budker Institute of Nuclear Physics, Siberian Branch of the Russian Academy of Science, pr. ac. Lavrentieva 11, Novosibirsk 630090, Russia
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Center for Northeast Asian Studies, Tohoku University, 41 Kawauchi, Aoba-ku, Sendai, Miyagi 980-8576, Japan
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Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Science, Lermontov Street 128, Irkutsk 664033, Russia
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Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA
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Center for Advanced Radiation Sources, University of Chicago, Chicago, IN 60637, USA
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Japan Synchrotron Radiation Research Institute, SPring-8, Kouto, Hyogo 678-5198, Japan
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Author to whom correspondence should be addressed.
Minerals 2019, 9(10), 599; https://doi.org/10.3390/min9100599
Received: 16 August 2019 / Revised: 20 September 2019 / Accepted: 26 September 2019 / Published: 30 September 2019
The phase diagrams of Na 2 CO 3 and K 2 CO 3 have been determined with multianvil (MA) and diamond anvil cell (DAC) techniques. In MA experiments with heating, γ -Na 2 CO 3 is stable up to 12 GPa and above this pressure transforms to P 6 3 /mcm-phase. At 26 GPa, Na 2 CO 3 - P 6 3 /mcm transforms to the new phase with a diffraction pattern similar to that of the theoretically predicted Na 2 CO 3 - P 2 1 /m. On cold compression in DAC experiments, γ -Na 2 CO 3 is stable up to the maximum pressure reached of 25 GPa. K 2 CO 3 shows a more complex sequence of phase transitions. Unlike γ -Na 2 CO 3 , γ -K 2 CO 3 has a narrow stability field. At 3 GPa, K 2 CO 3 presents in the form of the new phase, called K 2 CO 3 -III, which transforms into another new phase, K 2 CO 3 -IV, above 9 GPa. In the pressure range of 9–15 GPa, another new phase or the mixture of phases III and IV is observed. The diffraction pattern of K 2 CO 3 -IV has similarities with that of the theoretically predicted K 2 CO 3 - P 2 1 /m and most of the diffraction peaks can be indexed with this structure. Water has a dramatic effect on the phase transitions of K 2 CO 3 . Reconstruction of the diffraction pattern of γ -K 2 CO 3 is observed at pressures of 0.5–3.1 GPa if the DAC is loaded on the air. View Full-Text
Keywords: carbonate; diamond anvil cell; multi anvil apparatus; laser heating; resistive heating; global carbon cycle; indexing; density functional theory carbonate; diamond anvil cell; multi anvil apparatus; laser heating; resistive heating; global carbon cycle; indexing; density functional theory
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Gavryushkin, P.N.; Bekhtenova, A.; Lobanov, S.S.; Shatskiy, A.; Likhacheva, A.Y.; Sagatova, D.; Sagatov, N.; Rashchenko, S.V.; Litasov, K.D.; Sharygin, I.S.; Goncharov, A.F.; Prakapenka, V.B.; Higo, Y. High-Pressure Phase Diagrams of Na2CO3 and K2CO3. Minerals 2019, 9, 599.

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