Electronic band structure effects in the stopping of protons in copper

• Published in: Physical review. B 2016-10, Vol.94 (15), p.155403, Article 155403
• Main Authors: Quashie, Edwin E., Saha, Bidhan C., Correa, Alfredo A.
• Format: Article
• Language: English
• Subjects: Band structure of solids; Channeling; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Copper; Crossovers; Crystal structure; Density functional theory; Interatomic forces; Molecular dynamics; NUCLEAR PHYSICS AND RADIATION PHYSICS; Stopping power; Time dependence
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.94.155403

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.