Density functional theory calculations of continuum lowering in strongly coupled plasmas

Abstract

An accurate description of the ionization potential depression of ions in plasmas due to their interaction with the environment is a fundamental problem in plasma physics, playing a key role in determining the ionization balance, charge state distribution, opacity and plasma equation of state. Here we present a method to study the structure and position of the continuum of highly ionized dense plasmas using finite-temperature density functional theory in combination with excited-state projector augmented-wave potentials. The method is applied to aluminium plasmas created by intense X-ray irradiation, and shows excellent agreement with recently obtained experimental results. We find that the continuum lowering for ions in dense plasmas at intermediate temperatures is larger than predicted by standard plasma models and explain this effect through the electronic structure of the valence states in these strong-coupling conditions.

A Review of Studies on Strongly‐Coupled Coulomb Systems Since the Rise of DFT and SCCS‐1977

“…Experimental results for such 'level-shift' data are becoming available only now [38], while the DFT-theory had been available for decades [17,47]. Although DFT does not calculate energy levels, the difference in total internal energies between two configurations gives the energy of a spectral transition, and associated line shifts.…”

Measurement of Charged-Particle Stopping in Warm Dense Plasma

“…Dense plasmas in the warm-dense matter (WDM) regime, approximately solid density and tens of eV temperature, are of great interest as a probe of stopping-power theories, with broader physics relevance to nonequilibrium statistical mechanics [1], dense plasma transport properties [2][3][4], and bound-free transitions in WDM plasmas [5]. Accurate theory for bound-free transitions is required to interpret data obtained with common laser-plasma diagnostics including Thomson scattering [6] and opacity-based areal density techniques [7].…”

X-ray free-electron laser studies of dense plasmas

“…Son et al (2014) have developed a two-step Hartree-Fock-Slater model, which they claim also yields a better agreement with both the Orion and LCLS results. Vinko, Ciricosta & Wark (2014) have conducted a finite-temperature density functional theory (DFT) study of the electronic structure of ions in a dense plasma with a view to investigating the effect of continuum lowering. In this work, the electronic structure and the K-edges for the various charge states were seen to agree very well with the LCLS experiments; however, the authors were unable to reach the conditions of the Orion experiments due to the difficulty in using DFT methods at high temperatures.…”