Quartzlike carbon dioxide: An optically nonlinear extended solid at high pressures and temperatures

Area of Science:

• Materials Science
• High-Pressure Physics
• Solid-State Chemistry

Background:

• Carbon dioxide (CO2) exhibits diverse phases under varying pressure and temperature conditions.
• Understanding CO2 phase transitions is crucial for geochemistry and materials science.
• Previous research has identified several CO2 phases, but extended covalent solids remained elusive.

Purpose of the Study:

• To synthesize and characterize a new extended-solid phase of carbon dioxide.
• To investigate the structural and bonding properties of this novel CO2 phase.
• To explore the optical properties of the synthesized material.

Main Methods:

• Laser heating of carbon dioxide phase III in a diamond anvil cell at pressures above 40 GPa and temperatures of 1800 K.
• Quenching the synthesized material to ambient temperature while maintaining pressures above 1 GPa.
• Analysis of the material's vibration spectrum and optical nonlinearity.

Main Results:

• Successful synthesis of carbon dioxide phase V (CO2-V), an extended-solid phase.
• CO2-V can be quenched to ambient conditions above 1 GPa.
• Vibration spectrum of CO2-V resembles that of SiO2 quartz, indicating an extended covalent solid with C-O single bonds.
• CO2-V exhibits optical nonlinearity, generating second harmonic at 527 nm with ~0.1% efficiency.

Conclusions:

• A novel extended-solid phase of carbon dioxide (CO2-V) has been synthesized.
• CO2-V represents a new class of covalent network solids based on carbon and oxygen.
• The observed optical nonlinearity suggests potential applications in nonlinear optics and photonics.