Инд. авторы:	Lobanov S.S., Dong X., Martirosyan N.S., Samtsevich A.I., Stevanovic V., Gavryushkin P.N., Litasov K.D., Greenberg E., Prakapenka V.B., Oganov A.R., Goncharov A.F.
Заглавие:	Raman spectroscopy and x-ray diffraction of sp3 CaC O3 at lower mantle pressures
Библ. ссылка:	Lobanov S.S., Dong X., Martirosyan N.S., Samtsevich A.I., Stevanovic V., Gavryushkin P.N., Litasov K.D., Greenberg E., Prakapenka V.B., Oganov A.R., Goncharov A.F. Raman spectroscopy and x-ray diffraction of sp3 CaC O3 at lower mantle pressures // Physical Review B. - 2017. - Vol.96. - Iss. 10. - Art.104101. - ISSN 2469-9950.
Внешние системы:	DOI: 10.1103/PhysRevB.96.104101; РИНЦ: 31070500; SCOPUS: 2-s2.0-85029956113; WoS: 000408825700001;
Реферат:	eng: 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. © 2017 American Physical Society.
Ключевые слова:	ARAGONITE; PHASE; TRANSITION; CARBON; DOLOMITE; ELASTIC BAND METHOD; CRYSTAL-STRUCTURE PREDICTION; EARTHS LOWER MANTLE; CALCITE-III; MAGNESITE;
Издано:	2017
Физ. характеристика:	104101