Calculations of static and dynamic properties of hydrogen at warm dense matter conditions using quantum-trajectory molecular dynamics

The wave-packet approximation for solving many-body quantum dynamics allows for the time propagation of electronic degrees of freedom over ionic time scales and the investigation of non-adiabatic coupling between the electronic and ionic subsystems. We recently presented an extension of the formulation -- appropriate for quantum plasmas -- where the electron wave packet can be elongated in arbitrary directions [1]. The implementation of the model in the molecular dynamics framework LAMMPS is demonstrated to scale close to linear in particle number which in combination with MPI parallelisation allows for the treatment of a large number of particles needed for the computation of transport properties. Focusing on hydrogen and deuterium plasmas in the warm dense matter regime, the structural properties of the plasma within the model are compared with variational density matrix methods, path integral Monte Carlo and DFT-based methods, however, transport properties such as diffusion and viscosity derived from time-resolved quantities are also presented. The explicit treatment of the electron dynamics allows for a straightforward description of electron transport coefficients, such as electrical conductivity, without further approximation. Experimentally relevant quantities such as the dynamic structure factor can be computed directly from the time-resolved electron density without the need for the Chihara Decomposition where separate models are employed for the description of the adiabatic electron envelope around ions and the free electron motion.

[1] P. Svensson et al., Philos. Trans. R. Soc. A, 381:20220325 (2023)