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Silicon carbonate phase formed from carbon dioxide and silica under pressure
- Santoro, Mario, Gorelli, Federico, Haines, Julien, Cambon, Olivier, Levelut, Claire, Garbarino, Gaston
- Proceedings of the National Academy of Sciences of the United States of America 2011 v.108 no.19 pp. 7689-7692
- X-ray diffraction, carbon dioxide, carbonates, chemistry, infrared spectroscopy, porous media, silica, silicon, temperature, thermodynamics, zeolites
- The discovery of nonmolecular carbon dioxide under high-pressure conditions shows that there are remarkable analogies between this important substance and other group IV oxides. A natural and long-standing question is whether compounds between CO₂ and SiO₂ are possible. Under ambient conditions, CO₂ and SiO₂ are thermodynamically stable and do not react with each other. We show that reactions occur at high pressures indicating that silica can behave in a manner similar to ionic metal oxides that form carbonates at room pressure. A silicon carbonate phase was synthesized by reacting silicalite, a microporous SiO₂ zeolite, and molecular CO₂ that fills the pores, in diamond anvil cells at 18-26 GPa and 600-980 K; the compound was then temperature quenched. The material was characterized by Raman and IR spectroscopy, and synchrotron X-ray diffraction. The experiments reveal unique oxide chemistry at high pressures and the potential for synthesis of a class of previously uncharacterized materials. There are also potential implications for CO₂ segregation in planetary interiors and for CO₂ storage.