First-principles simulation of the electronic stopping power of He ions in Al at finite temperature

The electronic stopping power of low-energy He projectile particles moving through an Al film under channeling and off-channeling trajectories and its temperature dependence are studied by combining the time-dependent density-functional-theory method with molecular dynamics simulations. The results show that the effect of target temperature on target stopping power can be divided into two aspects which are derived from the target electron and target ion. Below 500 K, the effect of the target-electron temperature on target stopping power is almost negligible. The influence of the target-ion temperature on target stopping power can be divided into two aspects which are derived from the displacement and energy dissipation of target ions. The displacement of the target ion can result in two trends that change the target stopping power: (1) The target ion is closer to the center of lattice channel after displacement, which leads to the increase of target stopping power. (2) The target ion is farther away from the center of the lattice channel after displacement, which leads to the decrease in target stopping power. As the temperature increases, the target ions are more likely to appear farther away from the lattice channel than closer to the center of the lattice channel, so the average displacement of the target ions will lead to a decreasing trend of the target stopping power with the increase of temperature. Under the condition of a given ionic density in the target, the energy dissipation capacity of target ions increases with the increase of temperature, resulting in the tendency of the target stopping power to increase with the increase of temperature. Our calculated stopping powers are in good agreement with the experimental data and reproduced the deviation from velocity proportionality found in the experimental results for a He+ ion in Al, validating our approach and numerical implementation.