Investigating Mechanisms of State (De)Localization in Highly-Ionized Dense Plasmas

Predictions from standard ionisation potential depression (IPD) models have come under scrutiny in light of significant discrepancies with continuum lowering measurements at recent experiments involving highly-ionised dense plasmas. We attribute these discrepancies, in part, to difficulties in defining valence states as purely bound or purely free in plasmas with Debye lengths comparable to the inter-particle spacing. Here, we describe an approach to resolve this difficulty using finite-temperature density functional theory (FT-DFT). The "boundness" of a valence states is quantified by the spatial localization of its Kohn-Sham wavefunction, in a quantity we have termed ‘dimensionality’. When applied to ground state calculations of a simple metal and an ionic compound, the dimensionality correctly identifies localized and delocalized states. We apply the dimensionality to investigate the localization mechanism of isochoric heating in Al, Mg, and MgF₂. IPD levels are then extracted from the DFT calculations and compared with standard models and previous experiments.