Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
Raman spectroscopy and x-ray diffraction of sp3 CaC O3 at lower mantle pressures. / Lobanov, Sergey S.; Dong, Xiao; Martirosyan, Naira S. и др.
в: Physical Review B, Том 96, № 10, 104101, 01.09.2017.Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
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TY - JOUR
T1 - Raman spectroscopy and x-ray diffraction of sp3 CaC O3 at lower mantle pressures
AU - Lobanov, Sergey S.
AU - Dong, Xiao
AU - Martirosyan, Naira S.
AU - Samtsevich, Artem I.
AU - Stevanovic, Vladan
AU - Gavryushkin, Pavel N.
AU - Litasov, Konstantin D.
AU - Greenberg, Eran
AU - Prakapenka, Vitali B.
AU - Oganov, Artem R.
AU - Goncharov, Alexander F.
N1 - Publisher Copyright: © 2017 American Physical Society.
PY - 2017/9/1
Y1 - 2017/9/1
N2 - The exceptional ability of carbon to form sp2 and sp3 bonding states leads to a great structural and chemical diversity of carbon-bearing phases at nonambient conditions. Here we use laser-heated diamond-anvil cells combined with synchrotron x-ray diffraction, Raman spectroscopy, and first-principles calculations to explore phase transitions in CaCO3 at P>40GPa. We find that postaragonite CaCO3 transforms to the previously predicted P21/cCaCO3 with sp3-hybridized carbon at 105 GPa (∼30GPa higher than the theoretically predicted crossover pressure). The lowest-enthalpy transition path to P21/cCaCO3 includes reoccurring sp2 and sp3CaCO3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P21/cCaCO3 show an intense band at 1025cm-1, which we assign to the symmetric C-O stretching vibration based on empirical and first-principles calculations. This Raman band has a frequency that is ∼20% lower than the symmetric C-O stretching in sp2CaCO3 due to the C-O bond length increase across the sp2-sp3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.
AB - The exceptional ability of carbon to form sp2 and sp3 bonding states leads to a great structural and chemical diversity of carbon-bearing phases at nonambient conditions. Here we use laser-heated diamond-anvil cells combined with synchrotron x-ray diffraction, Raman spectroscopy, and first-principles calculations to explore phase transitions in CaCO3 at P>40GPa. We find that postaragonite CaCO3 transforms to the previously predicted P21/cCaCO3 with sp3-hybridized carbon at 105 GPa (∼30GPa higher than the theoretically predicted crossover pressure). The lowest-enthalpy transition path to P21/cCaCO3 includes reoccurring sp2 and sp3CaCO3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P21/cCaCO3 show an intense band at 1025cm-1, which we assign to the symmetric C-O stretching vibration based on empirical and first-principles calculations. This Raman band has a frequency that is ∼20% lower than the symmetric C-O stretching in sp2CaCO3 due to the C-O bond length increase across the sp2-sp3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.
KW - EARTHS LOWER MANTLE
KW - CRYSTAL-STRUCTURE PREDICTION
KW - ELASTIC BAND METHOD
KW - CALCITE-III
KW - CARBON
KW - TRANSITION
KW - PHASE
KW - ARAGONITE
KW - MAGNESITE
KW - DOLOMITE
UR - http://www.scopus.com/inward/record.url?scp=85029956113&partnerID=8YFLogxK
U2 - 10.1103/PhysRevB.96.104101
DO - 10.1103/PhysRevB.96.104101
M3 - Article
AN - SCOPUS:85029956113
VL - 96
JO - Physical Review B
JF - Physical Review B
SN - 2469-9950
IS - 10
M1 - 104101
ER -
ID: 9905977