Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution.

Area of Science:

• Materials Science
• Geochemistry
• Chemistry

Background:

• Extreme conditions enable the synthesis of unique materials.
• Carbon's distinct behavior in forming oxides compared to heavier group IV elements was previously assumed.
• Understanding oxide chemistry is crucial for materials, Earth, and planetary sciences.

Purpose of the Study:

• To synthesize a crystalline CO2-SiO2 solid solution.
• To investigate carbon's behavior in silica under high pressure and temperature.
• To explore the implications for oxide chemistry and the periodic table.

Main Methods:

• Reacting carbon dioxide and silica in a laser-heated diamond anvil cell at high pressures (16-22 GPa) and temperatures (>4,000 K).
• Utilizing X-ray diffraction to analyze the crystal structure and phase.
• Employing Raman spectroscopy to confirm material composition and structure.

Main Results:

• Successfully synthesized a crystalline CO2-SiO2 solid solution, showing carbon incorporation into silica.
• The material adopts a densely packed α-cristobalite structure (P4(1)2(1)2) with fourfold coordination for C and Si.
• The synthesized material is recoverable to ambient conditions.
• An average formula of C0.6(1)Si0.4(1)O2 was determined.

Conclusions:

• Carbon can be incorporated into silica under extreme conditions, forming a stable solid solution.
• The findings challenge the distinctness of carbon in oxide formation among group IV elements.
• This discovery impacts our understanding of oxide chemistry and has implications for materials science and planetary science.