Species Separation in Polystyrene Shock Release Evidenced by Molecular Dynamics Simulations and Laser Drive Experiments*

Materials shock release into vacuum generally happens in the targets of high-energy-density (HED) and inertial confinement fusion (ICF) experiments but has been challenging to study experimentally, theoretically, or computationally. Regular simulations based on single-fluid hydrodynamics may be questionable because of the ignorance of changes in materials chemistry, such as species separation as revealed in recent molecular-dynamics (MD) calculations of polystyrene (CH) upon release of a strong shock.[1] We performed extensive studies of the effect of shock strength and hydrogen isotope on CH shock release by combining MD simulations and laser drive experiments. Our simulations showed that species separation occured for strong shocks and more preferentially for CH with lighter hydrogen isotopes, consistent with experimental observations. Our simulations also considered preheated CH and showed enhanced velocities of the released low-density plasmas, which agreed with findings by hydrodynamics simulations. These results highlight the significant role of species separation in the release of compound materials and are significant for the design and analysis of HED and ICF experiments.

 

[1] S. Zhang and S. X. Hu, Phys. Rev. Lett 125, 105001 (2020)