Time-Dependent Density Functional Theory Applied to Average Atom Opacity

TL;DR

This study uses linear response time-dependent density functional theory to calculate plasma opacity of iron, chromium, and nickel, revealing limited channel mixing effects and suggesting other factors influence experimental opacity discrepancies.

Contribution

The paper applies linear response TD-DFT to plasma opacity calculations, highlighting the limited impact of channel mixing on opacity increases in these elements.

Findings

Opacity increase of 5-10% for iron due to channel mixing

No significant change in opacity trends for chromium and nickel

Channel mixing effects do not fully explain experimental opacity discrepancies

Abstract

We focus on studying the opacity of iron, chromium, and nickel plasmas at conditions relevant to experiments carried out at Sandia National Laboratories [J. E. Bailey et al., Nature 517, 56 (2015)]. We calculate the photo-absorption cross-sections and subsequent opacity for plasmas using linear response time-dependent density functional theory (TD-DFT). Our results indicate that the physics of channel mixing accounted for in linear response TD-DFT leads to an increase in the opacity in the bound-free quasi-continuum, where the Sandia experiments indicate that models under-predict iron opacity. However, the increase seen in our calculations is only in the range of 5-10%. Further, we do not see any change in this trend for chromium and nickel. This behavior indicates that channel mixing effects do not explain the trends in opacity observed in the Sandia experiments.