Dynamic Material Parameters in Molecular Dynamics and Hydrodynamic Simulations on Ultrashort-Pulse Laser Ablation of Aluminum

Abstract

Recent developments on the open-source Molecular Dynamics Code IMD from the Institute of Functional Materials and Quantum Technologies at Stuttgart University are reported. Whereas IMD supports laser ablation comprising the Two-Temperature Model by default, reliable simulation data mainly can be found for the femtosecond regime, since laser-matter interaction is implemented by the Lambert-Beer law solely. For laser-matter interaction in the picosecond regime, IMD algorithms were modified in order to enable the dynamic recalculation of the dielectric permittivity of each FD cell for every timestep following the corresponding implementation in the open-source hydrodynamic code Polly-2T from the Joint Institute of High Temperatures at the Russian Academy of Sciences, Moscow. Thus, optical changes in material and jet due the temporal evolution of temperature, density and mean charge are taken into account. Moreover, as implemented in Polly-2T as well, a dynamic model for the thermal conductivity of the electron gas is introduced in IMD to consider effects for a wide range of temperatures. Thus, hydrodynamic (HD) and Molecular Dynamics (MD) simulations are compared extracting the residual effects of the different model approaches which persist in a particle-based method (IMD) using an Embedded-Atom potential (EAM) and a finite cell based approach (Polly-2T) employing the semi-empirical equations of state (EOS) including ionization. Simulation results are compared with experimental results and literature data.