The frequency-dependent linear response of a plasma is studied in the finite-temperature Thomas-Fermi approximation, with electron dynamics described using Bloch hydrodynamics. The variational framework of average-atoms in a plasma is used. Extinctio
n cross-sections are calculated for several plasma conditions. Comparisons with a previously studied Thomas-Fermi Impurity in Jellium model are presented. An Ehrenfest-type sum rule, originally proposed in a full quantum approach is derived in the present formalism and checked numerically. This sum rule is used to define Bremsstrahlung and collective contributions to the extinction cross-section. It is shown that none of these is negligible. Each can constitute the main contribution to the cross-section, depending on the frequency region and plasma conditions. This result obtained in the Thomas-Fermi-Bloch case stresses the importance of the self consistent approach to the linear response in general. Some of the methods used in this study can be extended to the linear response in the quantum case.
A new code called VAAQP (Variational Average-Atom in Quantum Plasmas) is reported. The model as well as main results of previous studies are briefly recalled. The code is based on a new fully variational model of dense plasmas at equilibrium with qua
ntum treatment of all electrons. The code can calculate the Average Atom structure and the mean ionization from the variational equations respecting the virial theorem and without imposing the neutrality of the Wigner-Seitz sphere. The formula obtained for the electronic pressure is simple and does not require any numerical differentiation. A description of the principal features of the code is given. The thermodynamic consistency of the results obtained with VAAQP is shown by a comparison with another approach on the example of the aluminium 10 eV isotherm EOS curve. A first comparison to an INFERNO-type model is also presented.
The work on a new fully variational model of average-atom in quantum plasmas using a numerical code called VAAQP is reported. A brief description of the code is given. Application to aluminium at solid density and temperatures between 0.05 and 12 eV
is presented. Comparisons to results obtained using other approaches are also shown and discussed. The results prove the feasibility of the variational model in the warm dense matter regime. Effects of the variational treatment can lead in this region to significant differences with respect to existing models.
