TY - JOUR

T1 - Aragonite-II and CaCO3-VII

T2 - New high-pressure, high-temperature polymorphs of CaCO3

AU - Gavryushkin, Pavel N.

AU - Martirosyan, Naira S.

AU - Inerbaev, Talgat M.

AU - Popov, Zakhar I.

AU - Rashchenko, Sergey V.

AU - Likhacheva, Anna Yu

AU - Lobanov, Sergey S.

AU - Goncharov, Alexander F.

AU - Prakapenka, Vitali B.

AU - Litasov, Konstantin D.

N1 - Publisher Copyright: © 2017 American Chemical Society.

PY - 2017/12/6

Y1 - 2017/12/6

N2 - The importance for the global carbon cycle, the P-T phase diagram of CaCO3 has been under extensive investigation since the invention of the high-pressure techniques. However, this study is far from being completed. In the present work, we show the existence of two new highpressure polymorphs of CaCO3. The crystal structure prediction performed here reveals a new polymorph corresponding to distorted aragonite structure and named aragonite-II. In situ diamond anvil cell experiments confirm the presence of aragonite-II at 35 GPa and allow identification of another high-pressure polymorph at 50 GPa, named CaCO3-VII. CaCO3-VII is a structural analogue of CaCO3-P21/c-l, predicted theoretically earlier. The P-T phase diagram obtained based on a quasi-harmonic approximation shows the stability field of CaCO3-VII and aragonite-II at 30-50 GPa and 0- 1200 K. Synthesized earlier in experiments on cold compression of calcite, CaCO3-VI was found to be metastable in the whole pressure-temperature range.

AB - The importance for the global carbon cycle, the P-T phase diagram of CaCO3 has been under extensive investigation since the invention of the high-pressure techniques. However, this study is far from being completed. In the present work, we show the existence of two new highpressure polymorphs of CaCO3. The crystal structure prediction performed here reveals a new polymorph corresponding to distorted aragonite structure and named aragonite-II. In situ diamond anvil cell experiments confirm the presence of aragonite-II at 35 GPa and allow identification of another high-pressure polymorph at 50 GPa, named CaCO3-VII. CaCO3-VII is a structural analogue of CaCO3-P21/c-l, predicted theoretically earlier. The P-T phase diagram obtained based on a quasi-harmonic approximation shows the stability field of CaCO3-VII and aragonite-II at 30-50 GPa and 0- 1200 K. Synthesized earlier in experiments on cold compression of calcite, CaCO3-VI was found to be metastable in the whole pressure-temperature range.

KW - CRYSTAL-STRUCTURE PREDICTION

KW - X-RAY-DIFFRACTION

KW - PHASE-TRANSITIONS

KW - EARTHS MANTLE

KW - PROGRAM

KW - CARBON

KW - COMPRESSIBILITY

KW - REFINEMENT

KW - BEHAVIOR

KW - SYSTEM

UR - http://www.scopus.com/inward/record.url?scp=85042485202&partnerID=8YFLogxK

U2 - 10.1021/acs.cgd.7b00977

DO - 10.1021/acs.cgd.7b00977

M3 - Article

AN - SCOPUS:85042485202

VL - 17

SP - 6291

EP - 6296

JO - Crystal Growth and Design

JF - Crystal Growth and Design

SN - 1528-7483

IS - 12

ER -