  The interaction of energetic ions with the electronic and ionic system of
target materials is an interesting but challenging multi-scale problem and
understanding of the early stages after impact of heavy, initially charged ions
is particularly poor. At the same time, energy deposition during these early
stages determines later formation of damage cascades. We address the
multi-scale character by combining real-time time-dependent density functional
theory for electron dynamics with molecular dynamics simulations of damage
cascades. Our first-principles simulations prove that core electrons affect
electronic stopping and have an unexpected influence on the charge state of the
projectile. We show that this effect is absent for light projectiles, but
dominates the stopping physics for heavy projectiles. By parameterizing an
inelastic energy loss friction term in the molecular dynamics simulations using
our first-principles results, we also show a qualitative influence of
electronic stopping physics on radiation-damage cascades.

Materials Science