Density-functional approach to the absorption bands in a dense, partially ionized plasma

Density-functional theory (DFT) for finite temperature (T) is used to account for fluctuations of the transition energies in the average-atom model. These fluctuations lead to absorption bands in the bound-bound contribution to the total spectrum. The transition-energy fluctuations are related to the second derivative of the DFT functional Ω[n] with respect to the electron density n(r). In the numerical example (the spectrum and opacity of iron plasma at T=200 eV and solid density), the Thomas-Fermi (TF) form of ${\mathrm{\delta }}^2$Ω[n]/δn(r) δn(r ’) is taken. A comparison with a previous approach based on uncorrelated fluctuations around the TF atom clarifies the meaning of that approach. The numerical results indicate that the inclusion of interactions significantly diminishes the absorption bandwidths.