The effect of inelastic absorption on the elastic scattering of electrons and positrons in amorphous solids

The effect of inelastic absorption on the elastic scattering of electrons and positrons in amorphous solids is studied by means of an optical-potential model. Atomic electron densities and electrostatic potentials for atoms in solids are obtained from Dirac-Fock self-consistent electron densities for free atoms using Raith's muffin-tin model. In the case of electron projectiles, the exchange interaction is described by means of the local approximation of Furness and McCarthy. Correlation effects are modeled using a local-density approximation. The absorption potential, i.e., the imaginary part of the optical potential, is obtained from the local-density approximation, using the Born-Ochkur approximation and the Lindhard dielectric function to describe the interactions with a free-electron gas, and multiplied by an energy-independent empirical strength factor Aabs. With an appropriate selection of Aabs, the absorption cross section σabs, obtained from the partial-wave calculation with the aid of the optical theorem, practically equals the inelastic cross section for projectiles with energies from about 100 eV up to 1 MeV. The effects of inelastic absorption and aggregation are analyzed by comparison of differential cross sections, calculated with and without allowance of those effects, and by Monte Carlo simulations of electron elastic backscattering from solids. It is found that the effect of inelastic absorption on the scattering by atoms in solids is much weaker than for free atoms.