[en] We present an ad hoc method to correct the Coulomb logarithm of known models in order to match electron and ion temperature relaxation based on molecular dynamic simulations. A thermodynamic analysis is done. Numerical results are presented and discussed. (authors)

[en] We present ab initio simulations of liquid cerium in the framework of the LDA + U formulation. The liquid density has been determined self-consistently by searching for the zero pressure equilibrium state at 1320 K with the same set of parameters (U and J) and occupation matrices as those optimized for the γ phase. We have computed static and transport properties. The liquid produced by the simulations appears more structured than the available measurements. This raises questions regarding the ability of the theory to describe such a complex liquid. Conductivity calculations and temperature dependences are nevertheless in reasonable agreement with data.

[en] Ab initio molecular dynamics is used to compute the thermal conductivity of hydrogen at 80 g cm^-3 and temperature up to 800 eV. Pressures and ionic structure are compared with orbital-free calculations. Thermal conductivity is evaluated using the Kubo-Greenwood formula and is compared with models currently used in hydrodynamical simulations of inertial confinement fusion

[en] The extended first-principles molecular dynamics (Ext. FPMD) model introduced by Shen Zhang et al. has been implemented within the ab initio DFT software package ABINIT and is now publicly available. This model allows performing quantum molecular dynamics simulations (QMD) at high temperatures bypassing the well-known orbitals wall. QMD simulations can be done smoothly in the full range of temperatures from cold condensed matter to hot plasmas (>100 eV) passing by the warm dense matter regime. At high temperature, a minimum of Kohn-Sham orbitals is kept, allowing for deep ionization effects to manifest, such as the Schottky anomaly of the specific heat, in contrast with orbital-free approaches for which this effect is absent. Using the new 9.6 ABINIT version, we present extensive simulations of boron along isochores, from a few Kelvins to thousands of eVs, in the Gigabar regime and construct a table. The Hugoniot curve is found in close agreement with the FPEOS model, for a much lower computational intensity. An ionization analysis, deduced from the pressure or from the structure, emphasizes the crucial contribution of the very deep 1s shell in the maximum compression regime. (© 2022 Wiley‐VCH GmbH.)

[en] We present the story of full three-dimensional ab initio simulation techniques of dense plasmas based on the Kohn-Sham realization of the density functional theory, starting from early attempts using the Car-Parrinello method to the most recent approaches based on density matrix. We recall the decisive role played by two experiments, one on the Nova laser and the other at a much smaller scale, with pulsed electrical discharges. We emphasize that the essential roles of the Physics of Non-Ideal Plasmas (PNP) and Strongly Coupled Coulomb Systems (SCCS) conference series were most results, and simulation tools were presented and discussed under the benevolent presence of Vladimir Fortov. (© 2021 Wiley‐VCH GmbH)

[en] We present experimental results on pressure and resistivity on expanded nickel at a density of 0.1 g/cm³ and temperature of a few eV. These data, corresponding to the warm dense matter regime, are used to benchmark different theoretical approaches. A comparison is presented between fully three-dimensional quantum molecular dynamics (QMD) methods, based on density functional theory, with average atom methods, that are essentially one dimensional. In this regime the evaluation of the thermodynamic properties as well as electrical properties is difficult due to the concurrence of density and thermal effects which directly drive the metal-nonmetal transition. Experimental pressures and resistivities are given in a tabular form with temperatures deduced from QMD simulations.

[en] It is shown that a modified scheme of density functional theory, using the Thomas-Fermi kinetic energy functional for the electrons, is well suited to perform very-high-temperature molecular dynamics simulations on high-Z elements. As an example, iron on the principal Hugoniot is simulated up to 5 keV and 5 times the normal density, giving an equation of state in agreement with current models. Ionic structure is obtained and is given to an excellent level of precision by the structure of the one-component plasma computed for a coupling parameter corresponding to Thomas-Fermi ionization

[en] We measured the thermodynamical and transport properties of boron in the warm dense matter regime (15 000 K< T<25 000 K and ρ=0.094 g/cm³). Experimental data are compared with quantum molecular dynamics (QMD) simulations. We find a very good agreement between data and calculations, which permits us to transform experimental energies into temperatures, and allows us to compare conductivities with an average atom model coupled with a Kubo-Greenwood calculations. Contact is made between computationally intensive QMD simulation codes and fast average atom models

[en] We measured the thermodynamical and transport properties of aluminum-gold mixtures in the warm dense matter regime and for various concentrations. We compare these measurements with quantum molecular dynamics (QMD) simulations. We find that the calculated pressures and resistivities of both the mixtures and pure phases are in good agreement with the measurements. This further allows us to test the mixing rules usually employed to predict the properties of the mixed phases from the pure ones. We show, in this regime, that the partial densities mixing rule predicts the pressure of the mixture rather accurately but fails in its prediction of the optical conductivity. To improve this latter prediction, we find that we must invoke an isothermal-isobaric mixture rule to compute the pure phase contributions at the correct densities

[en] When hydrogen is mixed with heavy (high‐Z) elements, even as traces, such as iron in the sun, the plasma mixture transits from a weakly coupled state to the intermediate coupling regime of simultaneous weak and strong couplings due to charge asymmetry. In those circumstances, partial ionization is an important aspect to consider. We present a global approach for evaluating enhancement factors for thermonuclear reactions in such mixtures. We grounded our approach on extensive orbital free molecular dynamics (OFMD) simulations of hydrogen‐silver mixtures, chosen as a prototype of hydrogen-high‐Z mixtures, in a large range of temperature (100 < T < 1600 eV). By comparing a series of OFMD simulations to hyper‐netted chain calculations of effective binary ionic mixtures (eBIM), we set a general procedure for computing enhancement factors. The electron screening contribution is also included implicitly in the definition of the effective ionizations within the average atom framework. The agreement between the pair distribution functions of OFMD and eBIM validates a prescription in which each average atom representing a given species shares the same external electron density with the others (iso‐n${}_e$ rule). We checked that an interpolation formula between weak and strong couplings in BIM, due to Chugunov and DeWitt, is accurate enough to address the limit of extreme dilution of a heavy element. (© 2019 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)