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Phys. Rev. B 65, 104103 (2002) [6 pages]

Crystal structure of pseudo-six-fold carbon dioxide phase II at high pressures and temperatures

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C. S. Yoo1 *, H. Kohlmann2, H. Cynn1, M. F. Nicol2, V. Iota1, and T. LeBihan3
1Lawrence Livermore National Laboratory, University of California, Livermore, California 94551
2High Pressure Science and Engineering Center and Departments of Physics and Chemistry, University of Nevada Las Vegas, Las Vegas, Nevada 89154-4002
3European Synchrotron Radiational Facility, Grenoble, France

Received 29 November 2001; published 12 February 2002

The crystal structure of CO2-II is determined to be tetragonal P42/mnm with z=2, with evidence of some tetragonal-to-orthorhombic (Pnnm) disorder in the ab plane. In this structure, carbon atoms are pseudo-sixfold-coordinated by oxygens; two oxygens are at an elongated intramolecular C=O bond distance, 1.331(3) Å, and four are at a collapsed intermolecular distance, 2.377(2) Å, at the apices of highly distorted octahedral. Strong intermolecular association results in a large splitting of the symmetric stretching ν1 mode and in a high bulk modulus 131.5 GPa. At 11 GPa, CO2-II is about 6.8% denser than CO2-III (Cmca).


©2002 The American Physical Society

URL: http://link.aps.org/doi/10.1103/PhysRevB.65.104103
DOI: 10.1103/PhysRevB.65.104103
PACS: 64.70.Kb, 81.30.-t

* Email address: yoo1@llnl.gov

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