ENERGY-LOSS OF SLOW IONS - ONE-BAND CALCULATION FOR ALKALINE-METALS

The electronic energy loss has been calculated for low-energy ions in monovalent bcc crystals within first-order perturbation theory, as a function of impact parameter vector, velocity and direction of incidence. The electronic states in the solid are approximated using the Wigner-Seitz cellular method. Results for the two alkaline metals Li and Na are compared with predictions of existing models. The comparison indicates that the stopping power calculated from standard homogeneous electron gas theory is in quite good agreement with the average stopping power found from our more complete treatment. However, in the case of channeling we find that a simple scaling procedure allows for a much better prediction of the impact parameter dependence of the energy loss than the most widely used local-density approximation for an electron gas.