Molecular Dynamics Simulation of Strong Shock Waves Propagating in Dense Deuterium With the Effect of Excited Electrons

TL;DR

This study uses molecular dynamics with an electron force field to simulate shock waves in dense deuterium, revealing complex structures and charge effects due to electron excitation, relevant for inertial confinement fusion.

Contribution

It introduces a simulation approach that explicitly considers electron excitation effects in shock wave propagation in dense deuterium, enhancing understanding of complex shock structures.

Findings

Charge separation leads to large-scale net charges, not localized dipoles.

Molecular dissociation causes the 'bump' in the Hugoniot curve.

Electron excitation influences shock wave structure and energy dynamics.

Abstract

We present a molecular dynamics simulation of shock waves propagating in dense deuterium with the electron force field method [J. T. Su and W. A. Goddard, Phys. Rev. Lett. 99, 185003 (2007)], which explicitly takes the excitation of electrons into consideration. Non-equilibrium features associated with the excitation of electrons are systematically investigated. We show that chemical bonds in D$_2$ molecules lead to a more complicated shock wave structure near the shock front, compared with the results of classical molecular dynamics simulation. Charge separation can bring about accumulation of net charges on the large scale, instead of the formation of a localized dipole layer, which might cause extra energy for the shock wave to propagate. In addition, the simulations also display that molecular dissociation at the shock front is the major factor corresponding to the "bump" structure in the principal Hugoniot. These results could help to build a more realistic picture of shock wave propagation in fuel materials commonly used in the inertial confinement fusion.