A solid–solid phase transition in carbon dioxide at high pressures and intermediate temperatures
Despite its terrestrial abundance and astrochemical significance, many aspects of the phase diagram of solid carbon dioxide remain uncertain or unknown. The observed transition pressures from cubic to orthorhombic phase range widely from 2.5 GPa at 80 K to above 18 GPa at room temperature. The vibra...
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Published in | Nature communications Vol. 4; no. 1; p. 2647 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
London
Nature Publishing Group UK
2013
Nature Publishing Group |
Subjects | |
Online Access | Get full text |
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Summary: | Despite its terrestrial abundance and astrochemical significance, many aspects of the phase diagram of solid carbon dioxide remain uncertain or unknown. The observed transition pressures from cubic to orthorhombic phase range widely from 2.5 GPa at 80 K to above 18 GPa at room temperature. The vibrational Raman bands that appear at higher pressure and serve as a decisive proof of the existence of the orthorhombic phase have never been assigned. Here we introduce a general
ab initio
computational method that can predict the Gibbs free energies and thus phase diagrams of molecular crystals. Using this with second-order Møller—Plesset perturbation theory, we obtain the transition pressure of 13 GPa at 0 K with small temperature dependence, which is in line with many experiments. We also computationally reproduce the vibrational Raman bands and explain the pressure dependence of the structure parameters and Raman band positions of both phases quantitatively.
It is desirable for scientists to be able to predict the structures, spectra and phase diagrams of molecular crystals using
ab initio
computation. Li
et al
. demonstrate such an approach, which is able to determine the phase behaviour of solid carbon dioxide at a range of pressures and temperatures. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 2041-1723 2041-1723 |
DOI: | 10.1038/ncomms3647 |