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Title: Raman spectroscopy and x-ray diffraction of sp 3 CaC O 3 at lower mantle pressures

Abstract

The exceptional ability of carbon to form sp 2 and sp 3 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 CaC O 3 at P > 40 GPa . We find that postaragonite CaC O 3 transforms to the previously predicted P 2 1 / c CaC O 3 with sp 3 -hybridized carbon at 105 GPa ( ~ 30 GPa higher than the theoretically predicted crossover pressure). The lowest-enthalpy transition path to P2 1 / c CaC O 3 includes reoccurring sp 2 and sp 3 CaC O 3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P 2 1 / c CaC O 3 show an intense band at 1025 c m -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 % low-ymmetric C-O stretching in sp 2 CaC O 3 due to themore » C-O bond length increase across the sp 2 ~ sp 3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.« less

Authors:
; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFU.S. ARMY RESEARCHFOREIGNOTHER
OSTI Identifier:
1379431
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 96; Journal Issue: 10
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE

Citation Formats

Lobanov, Sergey S., Dong, Xiao, Martirosyan, Naira S., Samtsevich, Artem I., Stevanovic, Vladan, Gavryushkin, Pavel N., Litasov, Konstantin D., Greenberg, Eran, Prakapenka, Vitali B., Oganov, Artem R., and Goncharov, Alexander F. Raman spectroscopy and x-ray diffraction of sp3CaCO3 at lower mantle pressures. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.96.104101.
Lobanov, Sergey S., Dong, Xiao, Martirosyan, Naira S., Samtsevich, Artem I., Stevanovic, Vladan, Gavryushkin, Pavel N., Litasov, Konstantin D., Greenberg, Eran, Prakapenka, Vitali B., Oganov, Artem R., & Goncharov, Alexander F. Raman spectroscopy and x-ray diffraction of sp3CaCO3 at lower mantle pressures. United States. doi:10.1103/PhysRevB.96.104101.
Lobanov, Sergey S., Dong, Xiao, Martirosyan, Naira S., Samtsevich, Artem I., Stevanovic, Vladan, Gavryushkin, Pavel N., Litasov, Konstantin D., Greenberg, Eran, Prakapenka, Vitali B., Oganov, Artem R., and Goncharov, Alexander F. Fri . "Raman spectroscopy and x-ray diffraction of sp3CaCO3 at lower mantle pressures". United States. doi:10.1103/PhysRevB.96.104101.
@article{osti_1379431,
title = {Raman spectroscopy and x-ray diffraction of sp3CaCO3 at lower mantle pressures},
author = {Lobanov, Sergey S. and Dong, Xiao and Martirosyan, Naira S. and Samtsevich, Artem I. and Stevanovic, Vladan and Gavryushkin, Pavel N. and Litasov, Konstantin D. and Greenberg, Eran and Prakapenka, Vitali B. and Oganov, Artem R. and Goncharov, Alexander F.},
abstractNote = {The exceptional ability of carbon to form sp 2 and sp 3 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 CaC O 3 at P > 40 GPa . We find that postaragonite CaC O 3 transforms to the previously predicted P 2 1 / c CaC O 3 with sp 3 -hybridized carbon at 105 GPa ( ~ 30 GPa higher than the theoretically predicted crossover pressure). The lowest-enthalpy transition path to P2 1 / c CaC O 3 includes reoccurring sp 2 and sp 3 CaC O 3 intermediate phases and transition states, as revealed by our variable-cell nudged-elastic-band simulation. Raman spectra of P 2 1 / c CaC O 3 show an intense band at 1025 c m -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 % low-ymmetric C-O stretching in sp 2 CaC O 3 due to the C-O bond length increase across the sp 2 ~ sp 3 transition and can be used as a fingerprint of tetrahedrally coordinated carbon in other carbonates.},
doi = {10.1103/PhysRevB.96.104101},
journal = {Physical Review B},
number = 10,
volume = 96,
place = {United States},
year = {Fri Sep 01 00:00:00 EDT 2017},
month = {Fri Sep 01 00:00:00 EDT 2017}
}