Thermodynamic properties of the nonideal hydrogen plasmas: Comparison of different simulation techniques

Wave packet molecular dynamics–density functional theory method for non‐ideal plasma and warm dense matter simulations

“…Note that the density n e ≥ 10 22 cm −3 for all considered temperatures is already beyond the range of applicability for the classical MD and WPMD methods . At higher densities, these methods lead to a physically wrong particle distribution in the simulation cell, and we do not show their results in the figure.…”

“…Internal energy of hydrogen plasmas as a function of density for the temperatures of (a) T = 10,000 K, (b) T = 30,000 K and (c) T = 50,000 K obtained by the DPIMC method (black crosses), classical MD with the improved Kelbg potential (brown squares), WPMC (red diamonds), and WPMC‐DFT (blue circles). Black dashed lines show the formal degeneracy border Θ = ℏ 2 (3 π 2 n e ) 2/3 /(2 m e k B T ) = 1, and black horizontal line is the ideal gas energy E id = 1.5 T .…”

“…Unlike the classical methods, the WPMD‐DFT is able to reproduce the sharp increase of energy at densities around n = 10 24 cm –3 , related to the quantum degeneracy effects. Note that the original AWPMC method, taking exact exchange and no correlation effects into account, largely overestimates the energy in this high‐density range …”

“…The energy conservation is checked for the WPMD and WPMD-DFT simulations. The details of the classical MD simulations used here for comparison are given by Lavrinenko et al [24] We used the improved Kelbg interaction pseudopotential [25,26] for both electron-electron and electron-ion interactions. The system of N e = 4096 electrons and N i = 4096 ions with the periodic boundaries was brought to equilibrium with a given temperature using the Langevin thermostat.…”

“…Note that the original AWPMC method, taking exact exchange and no correlation effects into account, largely overestimates the energy in this high-density range. [24]…”