Electronic band structure effects in the stopping of protons in copper

Abstract:

We present an ab initio study of the electronic stopping power of protons in copper over a wide range of proton velocities v=0.02-10a.u. where we take into account nonlinear effects. Time-dependent density functional theory coupled with molecular dynamics is used to study electronic excitations produced by energetic protons. A plane-wave pseudopotential scheme is employed to solve the time-dependent Kohn-Sham equations for a moving ion in a periodic crystal. The electronic excitations and the band structure determine the stopping power of the material and alter the interatomic forces for both channeling and off-channeling trajectories. Our off-channeling results are in quantitative agreement with experiments, and at low velocity they unveil a crossover region of superlinear velocity dependence (with a power of ∼1.5) in the velocity range v=0.07-0.3a.u., which we associate to the copper crystalline electronic band structure. The results are rationalized by simple band models connecting two separate regimes. We find that the limit of electronic stopping v→0 is not as simple as phenomenological models suggest and it is plagued by band-structure effects.

Año de publicación:

2016

Keywords:

Fuente:

scopus