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

Abstract

A new wave packet molecular dynamics–density functional theory (WPMD‐DFT) method is proposed for atomistic simulations of non‐ideal plasma and warm dense matter. The method is based on the WPMD approach, where the electronic exchange and correlation effects are treated using an additional energy term taken from DFT. This term is calculated by integration over the mesh values of the wave packet density. The local density approximation is implemented so far. WPMD‐DFT is meant as a replacement for the anti‐symmetrized WPMD (AWPMD) method which is more time consuming and lacks electron correlation. In this paper, we compare the results obtained by WPMD‐DFT, WPMD, AWPMD, classical molecular dynamics, and path integral Monte Carlo methods for the internal energy of the hydrogen plasma in the temperature range 10–50 kK and electron number density from 1020 to 1024 cm−3. We also demonstrate the ability to handle the simultaneous dynamics of electrons and ions by calculating the electron–ion temperature relaxation. The scalability of the WPMD‐DFT method with the number of electrons is shown for implementations in central processing unit and graphical processing unit.

An Investigation into the Approximations Used in Wave Packet Molecular Dynamics for the Study of Warm Dense Matter

“…Future work will focus on improving the correlation part of this term, which could be modified to take into account local order [45], or exploiting the robust correlation functionals within DFT [50]. In addition, this work has been restricted to investigating low-temperature dense systems due to the serial implementation in MATLAB.…”

“…Despite our expanded basis, two approximations persist in our model; these are pairwise exchange and lack of correlation. The inclusion of correlation in such models is difficult and a decades-old problem in quantum mechanical many-body systems [49][50][51][52]. Motivated by eFF, we used a valence bond (VB) wave function to develop a simple pairwise correction term to account for these deficiencies.…”

Electron–ion temperature relaxation in nonideal plasmas: High accuracy classical molecular dynamics simulations

“…In reference [16], the application of the WPMD based on electron force field (eFF) with specially configured wave packet width restraint leads to much lower relaxation rate for quantum electrons than predicted by the classical MD. Some modifications of WPMD to account for antisymmetrization of the electron wave function may be considered parameterless [41][42][43] but require more computational effort compared to the classical MD or original WPMD. The use of WPMD and its modifications requires careful choice of the boundary conditions.…”

“…[44] We consider the results of the current work described in the next section as a useful reference for our future study of the relaxation rate with the help of the original WPMD and the improved WPMD-DFT method, where the exchange-correlation term is calculated using the density functional theory. [42,43]…”

Ion modes in dense ionized plasmas through nonadiabatic molecular dynamics

“…For many systems, EFF is found to have an exchange energy comparable to unrestricted Hartree-Fock [35]. There have been some recent efforts to include more robust correlation functionals derived from DFT in WPMD [37], but correlation is not currently treated in EFF.…”