Ab initio calculations of electron inelastic mean free paths and stopping powers

A method is presented for first-principles calculations of electron inelastic mean free paths and stopping powers in condensed matter over a broad energy range. The method is based on ab initio calculations of the dielectric function in the long wavelength limit using a real-space Green's function formalism, together with extensions to finite momentum transfer. From these results we obtain the energy-loss function and related quantities such as optical-oscillator strengths and mean excitation energies. From a many-pole representation of the dielectric function we then obtain the electron self-energy and inelastic mean free paths. Finally, using our calculated dielectric function and the optical-data model of Fernandez-Varea [Nucl. Instr. and Meth. B 229, 187 (2005)], we obtain collision stopping powers and penetration ranges. The results are consistent with semiempirical approaches and with experiment.