We show that atomistic first-principles calculations based on real-time propagation within time-dependent density functional theory are capable of accurately describing electronic stopping of light projectile atoms in metal hosts over a wide range of projectile velocities. In particular, we employ a plane-wave pseudopotential scheme to solve time-dependent Kohn-Sham equations for representative systems of H and He projectiles in crystalline aluminum. This approach to simulate non-adiabatic electron-ion interaction provides an accurate framework that allows for quantitative comparison with experiment without introducing ad-hoc parameters such as effective charges, or assumptions about the dielectric function. Our work clearly shows that this atomistic first-principles description of electronic stopping is able to disentangle contributions due to tightly bound semicore electrons and geometric aspects of the stopping geometry (channeling vs. off-channeling) in a wide range of projectile velocities.

Excitonic effects in optical spectra and electron-hole pair excitations are described by solutions of the Bethe-Salpeter equation (BSE) that accounts for the Coulomb interaction of excited electron-hole pairs. Although for the computation of excitonic optical spectra in an extended frequency range efficient methods are available, the determination and analysis of individual exciton states still requires the diagonalization of the electronhole HamiltonianĤ. We present a numerically efficient approach for the calculation of exciton states with quadratically scaling complexity, which significantly diminishes the computational costs compared to the commonly used cubically scaling direct-diagonalization schemes. The accuracy and performance of this approach is demonstrated by solving the BSE numerically for the Wannier-Mott two-band model in k space and the semiconductors MgO and InN. For the convergence with respect to the k-point sampling a general trend is identified, which can be used to extrapolate converged results for the binding energies of the lowest bound states.

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Using quasiparticle band structures based on modern electronic-structure theory, we calculate the branch-point energies for zinc blende ͑GaN, InN͒, rocksalt ͑MgO, CdO͒, wurtzite ͑AlN, GaN, InN, ZnO͒, and rhombohedral crystals ͑In 2 O 3 ͒. For InN, CdO, ZnO, and also In 2 O 3 the branch-point energies are located within the lowest conduction band. These predictions are in agreement with observations of surface electron accumulation ͑InN, CdO͒ or conducting behavior of the oxides ͑ZnO, In 2 O 3 ͒. The results are used to predict natural band offsets for the materials investigated.