First-principles study of the electronic stopping power of Zn for protons

The electronic stopping power of Zn for energetic protons is studied by using a nonequilibrium approach based on real-time time-dependent density-functional theory combined with molecular dynamics simulations. We calculated the electronic stopping power of protons traveling along two channeling trajectories depending on the impact parameter and off-channeling trajectories, and revealed the mechanism for d-electron excitation. In the low-velocity range, we reproduced not only the velocity proportionality of the stopping power of Zn for protons, but also the smooth transition between two velocity proportionality regimes, which is ascribed to the gradually increasing efficiency for d-electron excitation. The off-channeling electronic stopping power is in a good agreement with experimental data in the low and middle-velocity regimes. Our results showed that the contribution of d-electron excitation to the electronic stopping is remarkable in the high-velocity regime.