Extended Mermin Method for Calculating the Electron Inelastic Mean Free Path

We propose an improved method for calculating electron inelastic mean free paths (IMFPs) in solids from experimental energy-loss functions (ELFs) based on the Mermin dielectric function. The “extended Mermin” method is much simpler over a wide energy range than the traditional approach. We employ negative oscillators to obtain accurate ELFs; these naturally preserve two important sum rules when extending to infinite momentum transfer. Excellent agreement is found between calculated IMFPs for Cu and experimental measurements from elastic peak electron spectroscopy. Notably improved fits to x-ray absorption fine structure measurements of Cu and Mo at low energy illustrate the method’s strength.