Variational average atom in quantum plasmas (VAAQP)—first numerical results

A new code called VAAQP (variational average atom in quantum plasmas) is briefly described and its first results in the case of aluminium at solid density and temperatures between 0.05 and 12 eV are reported. The code is based on a new fully variational approach to plasmas at local equilibrium with both bound and free electrons treated quantum mechanically. This model which is derived from two first terms of the cluster expansion appears to be the quantum extension of the well-known atom-in-cell model based on the Thomas–Fermi theory (Thomas–Fermi average atom) that has been proposed in 1949 by Feynman, Metropolis and Teller. Similar to the case of Feynman et al's model the VAAQP approach, due to its fully variational character, respects the virial theorem and uses a simple formula for the electronic pressure. Comparisons to results obtained using other approaches are also shown and discussed in the aluminium case. The results confirm the feasibility of the quantum variational model in the warm dense matter regime. Effects of the variational treatment can lead in this regime to significant differences with respect to existing non-variational models.