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High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems
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Thermodynamically stable phases of carbon at multiterapascal pressures
Miguel Martinez-Canales1, Chris J Pickard, Richard J Needs
1Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom. miguel.c.martinez@ucl.ac.uk
Physical Review Letters
|March 10, 2012
Summary
This study explores carbon phases under extreme pressures up to 1 petapascal using advanced computational methods. New high-pressure carbon structures, including simple hexagonal and face-centered cubic electride, were predicted.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Computational Chemistry
Background:
- Understanding carbon's behavior under extreme pressure is crucial for materials science.
- Previous theoretical studies suggested specific phase transitions at high pressures.
Purpose of the Study:
- To investigate the structural phases of carbon at ultra-high pressures up to 1 petapascal.
- To identify novel carbon allotropes and their transition pressures.
Main Methods:
- Utilized first-principles density-functional-theory (DFT) calculations.
- Employed a structure searching algorithm to explore the potential energy surface.
- Simulated carbon under pressures ranging from ambient to 1 petapascal.
Main Results:
- Confirmed the diamond → BC8 → simple cubic transition sequence at lower pressures.
- Predicted a novel soft-phonon driven transition to a simple hexagonal structure at 6.4 terapascals.
- Identified further transitions to face-centered cubic electride (21 TPa), double hexagonal close packed (270 TPa), and body-centered cubic (650 TPa) structures.
Conclusions:
- The study provides a comprehensive map of carbon's high-pressure phases.
- Predicts new, stable carbon structures at pressures exceeding previous theoretical limits.
- Highlights the importance of computational methods in discovering novel materials under extreme conditions.
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