Role of Electronic Effects in Compression Shockwave Molecular Dynamics Simulations

Experimental determination of material properties subjected to rapid compression relies on indirect measurements that use utilise tabulated equation of states for the materials being studied. Moreover, the tables being used describe the materials in equilibrium statues, which might not be fully achieved in the fast compression conditions. Finally, to achieve very high compression ratios that are of interest for example for planetary science, the experimental setups able to reach are physically very large, such as NIF, and expensive to use for gathering large amounts of data for statistical purposes.

An alternative method for studying the materials undergoing a compression shockwave relies on computational modelling. The various modelling techniques range from quantum mechanical, such as density functional theory (DFT), which can provide materials properties for small smaples in equilibrium conditions, to atomistic molecular dynamics (MD) and continuum modelling, such as finite element method. Also, it is possible to parameterise the models used to model the shockwave dynamics with MD with the data collected from DFT. Nevertheless, the MD methods, widely used, lack the electronic effects present in the material. It is well known that in metallic systems the energy can be transferred from ions to electrons and vice versa. These effects are following: electron-phonon coupling, which is dominant near equilibrium, and electronic stopping, that acts in non-equilibrium conditions. Recently, we have been able to develop a model based on Langevin dynamics with spatial correlations that has been shown to be able to realistically capture both the electron-phonon as well as electronic stopping processes in atomistic MD simulations.

In this study we use our new method to study the materials response to compression shockwaves. We are going to study single crystal copper along three main crystallographic directions with electronic effects. We analyse the temperature profiles in the sample as well as crystal structure behind the shockwave.