Quantum mechanical simulations of electronic stopping in metals

The close spacing of electron energy levels at the Fermi surface of a metal allows for a ready exchange of energy between ionic and electronic subsystems. In molecular dynamics (MD) simulations of fast moving ions, the heat transfer to electrons is sometimes modelled as a frictional force that slows the ions. Quantum mechanical simulations lay bare these processes and reveal how best to characterise electronic friction and heating for direct incorporation into MD. In this paper, we discuss the limitations of the description of electronic damping as a viscous force, the validity of the two-temperature model, and how the non-adiabatic movement of electrons between bonds leads to directional stopping.