Electronic stopping for protons and {α} particles from first-principles electron dynamics: The case of silicon carbide

We present the first-principles determination of electronic stopping power for protons and {\alpha} particles in a semiconductor material of great technological interest: silicon carbide. The calculations are based on nonequilibrium simulations of the electronic response to swift ions using real-time, time-dependent density functional theory (RT-TDDFT). We compare the results from this first-principles approach to those of the widely used linear response formalism and determine the ion velocity regime within which linear response treatments are appropriate. We also use the nonequilibrium electron densities in our simulations to quantitatively address the longstanding question of the velocity-dependent effective charge state of projectile ions in a material, due to its importance in linear response theory. We further examine the validity of the recently proposed centroid path approximation for reducing the computational cost of acquiring stopping power curves from RT-TDDFT simulations.