Two-temperature pair potentials and phonon spectra for simple metals in the warm dense matter regime

Abstract

We develop ion-ion pair potentials for Al, Na and K for densities and temperatures relevant to the warm-dense-matter (WDM) regime. Furthermore, we emphasize non-equilibrium states where the ion temperature $T_i$ differs from the electron temperature $T_e$. This work focuses mainly on ultra-fast laser-metal interactions where the energy of the laser is almost exclusively transferred to the electron sub-system over femtosecond time scales. This results in a two-temperature system with $T_e>T_i$ and with the ions still at the initial room temperature $T_i=T_r$. First-principles calculations, such as density functional theory (DFT) or quantum Monte Carlo, are as yet not fully feasible for WDM conditions due to lack of finite-$T$ features, e.g. pseudopotentials, and extensive CPU time requirements. Simpler methods are needed to study these highly complex systems. We propose to use two-temperature pair potentials $U_{ii}(r,T_i,T_e)$ constructed from linear-response theory using the non-linear electron density $n(\mathbf{r})$ obtained from finite-$T$ DFT with a single ion immersed in the appropriate electron fluid. We compute equilibrium phonon spectra at $T_r$ which are found to be in very good agreement with experiments. This gives credibility to our non-equilibrium phonon dispersion relations which are important in determining thermophysical properties, stability, energy-relaxation mechanisms and transport coefficients.

arXiv commentInternational Conf. on Strongly-Coupled Coulombo Systems (SCCS) 2014

References in corpus (5)

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• A simple classical mapping of the spin-polarized quantum electron gas: distribution functions and local field corrections
• Exchange-correlation energy for the 3D homogeneous electron gas at arbitrary temperature
• Comparison of Density Functional Approximations and the Finite-temperature Hartree-Fock Approximation in Warm Dense Lithium
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Cited by in corpus (5)

• Ion-ion dynamic structure factor, acoustic modes and equation of state of two-temperature warm dense aluminum
• Equation of state, phonons, and lattice stability of ultra-fast warm dense matter
• Pair potentials for warm dense matter and their application to x-ray Thomson scattering in aluminum and beryllium
• A critical assessment of models of pair-interactions and screening used in analyzing recent warm-dense matter (WDM) experiments
• The dynamic conductivity and the plasmon profile of Aluminum in the ultra-fast-matter regime; an analysis of recent X-ray scattering data from the LCLS