Equivalence between pressure- and structure-defined ionization in hot dense carbon

Area of Science:

• Plasma physics
• Computational physics
• Materials science

Background:

• Accurate determination of ionization in hot dense matter is crucial but challenging.
• Existing average atom models show inconsistencies with electronic transport properties from quantum molecular dynamics simulations.

Purpose of the Study:

• Propose new definitions for ionization based on plasma structure and pressure.
• Investigate the ionization of carbon under hot dense conditions.
• Compare new definitions with existing models and experimental data.

Main Methods:

• Utilized effective one-component plasma (eOCP) concept and pair distribution functions (PDF).
• Introduced definitions based on total pressure and electronic pressure models.
• Performed extensive simulations using Ext. First principles molecular dynamics (Fpmd) and Spectral quadrature DFT (Sqdft).

Main Results:

• Demonstrated the equivalence of the proposed ionization definitions for carbon.
• Compared simulation results with the average-atom code Qaam, revealing discrepancies.
• Interpreted deviations from eOCP as indicators of bonding onset in the system.

Conclusions:

• The new definitions provide a more accurate measure of ionization in hot dense plasmas.
• Disagreements highlight limitations of average atom models and muffin-tin approximations.
• The study offers a refined understanding of plasma behavior and bonding under extreme conditions.