First-principles molecular dynamics study of the inner electron excitation effect in the interaction of lithium ions with silicon

Abstract Within the theoretical framework of time-dependent density functional theory (TDDFT) combined with non-adiabatic dynamics, the microscopic mechanism of electronic excitation of silicon induced by energetic lithium ions and its contribution to electronic stopping were investigated by constructing optimized normconserving Vanderbilt pseudopotential (ONCV) models. Our results showed that at v < 3.0 a.u., the electronic stopping power ( S e ) is dominated by the charge state of Li ions, which is strongly influenced by the inner-shell electron excitation of Si. The S e is governed by the inner-shell electron excitations of both Li ions and Si beyond this velocity, and the contribution of inner-shell electron excitation of projectile Li ions is more pronounced than that of Si. By comparing the charge states of Li ions in channeling and off-channeling trajectories, it was revealed that the high charge state of Li 3+ ions is responsible for the enhanced S e in the channeling geometry. This study demonstrates that only by considering the inner-shell electron excitations of both Si and Li can the S e be accurately described across the entire velocity range.