Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure1–9. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, nonmolecular formof CO2 has so far been described only as a result of first-principles simulations9. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call ‘a-carbonia’. The compression of the molecular phase III of CO2 between 40 and 48 GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680 K show the progressive formation of C–O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-ofthe- art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics9, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal networkforming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2.

Amorphous silica-like carbon dioxide / M. SANTORO; F.A. GORELLI; R. BINI; G. RUOCCO; S. SCANDOLO; W. CRICHTON. - In: NATURE. - ISSN 0028-0836. - STAMPA. - 41:(2006), pp. 857-860. [10.1038/nature04879]

Amorphous silica-like carbon dioxide

SANTORO, MARIO;BINI, ROBERTO;
2006

Abstract

Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure1–9. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, nonmolecular formof CO2 has so far been described only as a result of first-principles simulations9. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call ‘a-carbonia’. The compression of the molecular phase III of CO2 between 40 and 48 GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680 K show the progressive formation of C–O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-ofthe- art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics9, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal networkforming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2.
2006
41
857
860
M. SANTORO; F.A. GORELLI; R. BINI; G. RUOCCO; S. SCANDOLO; W. CRICHTON
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/201730
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