Applicability of the classical molecular dynamics method to study x-ray irradiated molecular systems

Classical molecular dynamics (MD) has been successfully applied to model radiation-induced dynamics of highly ionized assemblies of atoms, including the dynamics of electrons, released during ionization processes. Here we test the applicability of a classical MD scheme in a yet unexplored regime: for a strongly bound molecular system represented by buckminsterfullerene, C-60, singly ionized by an x-ray pulse. We show MD simulation results obtained for electron and ion spectra, and compare them to existing experimental data from synchrotron experiments. We identify the sources of discrepancies between the classical simulations and experiments, and discuss possible improvements of the model. Our calculations establish limits for the applicability of classical MD simulations to x-ray irradiated systems. These classical simulations are much more computationally efficient than any rigorous quantum calculations, and are, therefore, often the only option. The conclusions obtained can be useful for planning computational studies of irradiated large molecular assemblies.