Molecular Dynamics Simulations of Shocks Including Electronic Heat Conduction and Electron-Phonon Coupling

Abstract

Abstract. Shocks are often simulated using the classical molecular dynamics (MD) method in which the electrons are not included explicitly and the interatomic interaction is described by an effective potential. As a result, the fast electronic heat conduction in metals and the coupling between the lattice vibrations and the electronic degrees of freedom can not be represented. Under conditions of steep temperature gradients that can form near the shock front, however, the electronic heat conduction can play an important part in redistribution of the thermal energy in the shocked target. We present the first atomistic simulation of a shock propagation including the electronic heat conduction and electronphonon coupling. The computational model is based on the two-temperature model (TTM) that describes the time evolution of the lattice and electron temperatures by two coupled non-linear differential equations. In the combined TTM-MD method, MD substitutes the TTM equation for the lattice temperature. Simulations are performed with both MD and TTM-MD models for an EAM Al target shocked at 300 kbar. The target includes a tilt grain boundary, which provides a region where shock heating is more pronounced and, therefore, the effect of the electronic heat conduction is expected to be more important. We find that the differences between the predictions of the MD and TTM-MD simulations are significantly smaller as compared to the hydrodynamics calculations performed at similar conditions with and without electronic heat conduction.

Molecular Dynamics Study of Short-Pulse Laser Melting, Recrystallization, Spallation, and Ablation of Metal Targets

“…First applications of the TTM-MD model have already provided insights into the microscopic mechanisms of laser melting and disintegration of Ni and Au films [8][9][10][11], photomechanical spallation of Cu and Ni targets [12,13]. The hybrid TTM-MD model was also used in a recent study of shock-induced heating and melting of a grain boundary region in an Al crystal [14] and in the analysis of the kinetics and channels of laser energy redistribution in a Ni target irradiated by a short laser pulse [15].…”

Molecular dynamics simulation of shock waves in laser-material interaction

“…Zhigilei (2003) investigated the dynamics of the early stages of the ablation plume formation and the mechanisms of cluster ejection in large-scale molecular dynamics simulations (more than 1 million molecules). Ivanov et al (2003) presented the first atomistic simulation of a shock propagation including the electronic heat conduction and electronphonon coupling. Their computational model was based on the two-temperature model that describes the time evolution of the lattice and electron temperatures by two coupled non-linear differential equations.…”