Calculation of inelastic mean free path and stopping power for electrons in solids from an optical-data model

The numerical calculation of electron inelastic mean free path and stopping power from an optical data model recently proposed by Fernandez-Varea et al. is described. Explicit expressions for the one electron total cross sections of the two modes model of the free electron gas and the delta oscillator are derived. The inelastic mean free path and the stopping power are obtained as integrals of these one electron total cross sections weighted by the optical oscillator strength. The integrals can be easily evaluated, with a selected accuracy, by using the FORTRAN 77 subroutine GABQ described, which implements a 20 point Gauss Adaptive Bipartition Quadrature method. Source listings of FORTRAN 77 subroutines to compute the one electron total cross sections are also given.