Six-fold coordinated carbon dioxide VI
| Autor: | Jae-Hyun Klepeis, V. Iota, Choong-Shik Yoo, William J. Evans, Zsolt Jenei, Hyunchae Cynn |
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| Rok vydání: | 2006 |
| Předmět: |
Silicon
Mechanical Engineering chemistry.chemical_element General Chemistry Crystal structure Condensed Matter Physics Isothermal process Crystallography chemistry.chemical_compound Molecular solid Tridymite chemistry Mechanics of Materials Covalent bond Carbon dioxide Organic chemistry General Materials Science Phase diagram |
| Zdroj: | Nature Materials. 6:34-38 |
| ISSN: | 1476-4660 1476-1122 |
| Popis: | Under standard conditions, carbon dioxide (CO2) is a simple molecular gas and an important atmospheric constituent, whereas silicon dioxide (SiO2) is a covalent solid, and one of the fundamental minerals of the planet. The remarkable dissimilarity between these two group IV oxides is diminished at higher pressures and temperatures as CO2 transforms to a series of solid phases, from simple molecular to a fully covalent extended-solid V, structurally analogous to SiO2 tridymite. Here, we present the discovery of an extended-solid phase of CO2: a six-fold coordinated stishovite-like phase VI, obtained by isothermal compression of associated CO2-II (refs 1,2) above 50 GPa at 530–650 K. Together with the previously reported CO2-V (refs 3–5) and a-carbonia6, this extended phase indicates a fundamental similarity between CO2 (a prototypical molecular solid) and SiO2 (one of Earth’s fundamental building blocks). We present a phase diagram with a limited stability domain for molecular CO2-I, and suggest that the conversion to extended-network solids above 40–50 GPa occurs via intermediate phases II (refs 1,2), III (refs 7,8) and IV (refs 9,10). The crystal structure of phase VI suggests strong disorder along the c axis in stishovite-like P42/m n m, with carbon atoms manifesting an average six-fold coordination within the framework of s p3 hybridization. |
| Databáze: | OpenAIRE |
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