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Liquid-liquid phase transition in elemental carbon: a first-principles investigation
Christine J Wu1, James N Glosli, Giulia Galli
1Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94550, USA.
Physical Review Letters
|September 13, 2002
Summary
Elemental carbon does not exhibit a liquid-liquid phase transition (LLPT). First-principles simulations reveal a continuous fluid evolution, unlike empirical models that suggested an LLPT in carbon.
Area of Science:
- Condensed matter physics
- Materials science
- Computational chemistry
Background:
- Recent theoretical studies proposed elemental carbon as a candidate for a liquid-liquid phase transition (LLPT).
- Empirical calculations suggested the existence of LLPT in carbon under specific temperature and pressure conditions.
Purpose of the Study:
- To investigate the possibility of a liquid-liquid phase transition (LLPT) in elemental carbon.
- To compare the results of first-principles simulations with those obtained from empirical calculations.
Main Methods:
- First-principles molecular dynamics simulations were employed.
- Simulations were conducted in the temperature and pressure range where LLPT was previously suggested.
Main Results:
- No evidence of a liquid-liquid phase transition (LLPT) in elemental carbon was found.
- Simulations indicated a continuous transformation of the liquid carbon structure.
- The liquid evolved from sp-bonded to sp(2)-like and sp(3)-like fluids with increasing pressure above the graphite melting line.
Conclusions:
- First-principles simulations contradict previous empirical findings regarding LLPT in carbon.
- Empirical potentials are inadequate for accurately describing the complex electronic behavior of condensed carbon phases.
- The study highlights the importance of quantum mechanical approaches for understanding carbon's phase behavior.