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Free-energy model for fluid helium at high density.
Christophe Winisdoerffer1, Gilles Chabrier
1Theoretical Astrophysics Group, University of Leicester, Leicester, LE1 7RH, United Kingdom. cwinisdo@ens-lyon.fr
Summary
We developed a new model for dense fluid helium, predicting abrupt pressure ionization from atomic to fully ionized states. This research aids understanding of helium
Area of Science:
- Thermodynamics
- Plasma Physics
- Astrophysics
Background:
- Dense fluid helium exhibits complex thermodynamic properties across various states.
- Understanding helium's behavior is crucial for astrophysical objects like giant planets.
Purpose of the Study:
- To develop a semianalytical free-energy model for dense fluid helium.
- To characterize thermodynamic properties from atomic to fully ionized regimes.
- To compute the phase diagram and ionization contours of dense helium.
Main Methods:
- Employed a free-energy minimization method.
- Incorporated contributions accounting for atomic, ionic, and electron correlations.
- Extended calculations over a wide range of density and temperature.
Main Results:
- Predicted abrupt pressure ionization at densities >= 10 g/cm³ (>= 20 Mbar).
- Indicated a transition directly from atomic He to a strongly ionized state (He2+).
- Mapped the phase diagram of dense fluid helium, including ionization contours.
Conclusions:
- The model provides a framework for studying helium's high-density properties, including metallization.
- Phase diagram predictions guide future experiments and first-principle calculations.
- Characterizing helium's phase diagram has significant implications for astrophysics.