In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 109, No. 14 ( 2012-04-03), p. 5176-5179
Abstract:
Non molecular CO 2 has been an important subject of study in high pressure physics and chemistry for the past decade opening up a unique area of carbon chemistry. The phase diagram of CO 2 includes several non molecular phases above 30 GPa. Among these, the first discovered was CO 2 -V which appeared silica-like. Theoretical studies suggested that the structure of CO 2 -V is related to that of β-cristobalite with tetrahedral carbon coordination similar to silicon in SiO 2 , but reported experimental structural studies have been controversial. We have investigated CO 2 -V obtained from molecular CO 2 at 40–50 GPa and T 〉 1500 K using synchrotron X-ray diffraction, optical spectroscopy, and computer simulations. The structure refined by the Rietveld method is a partially collapsed variant of SiO 2 β-cristobalite, space group , in which the CO 4 tetrahedra are tilted by 38.4° about the c -axis. The existence of CO 4 tetrahedra (average O-C-O angle of 109.5°) is thus confirmed. The results add to the knowledge of carbon chemistry with mineral phases similar to SiO 2 and potential implications for Earth and planetary interiors.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1118791109
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2012
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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