ELF dielectric functions for various materials.

Data for the energy loss function (ELF) of selected materials compiled from various publications.

The imaginary part of the inverse of the dielectric function, Im{−1/ε(k,hω)}, denoted the energy loss function (ELF), is the leading function that describes the material response to account for energy losses of swift electrons in matter. For this reason, it is a practical advantage to express the dielectric function in the form of a parametrized ELF, instead of the dielectric function itself, as input for the calculation of inelastic scattering cross sections. Here the ELF  is expressed as a sum of Drude-Lindhard type oscillators  (see e.g. Yubero F, Sanz JM, Ramskov B, Tougaard S. Model for quantitative analysis of reflection-electron-energy-loss spectra: Angular dependence. Phys Rev B. 1996;53:9719-9727)

The ELF data describe the dielectric properties of materials.
It may be applied to calculate energy loss processes of fast electrons moving in a material as well as in geometries met in REELS, XPS and AES where the effect of the surface and a static core hole are included (see e.g. QUEELS-software that can be downloaded at: doi: 10.5281/zenodo.6022426)

The data structure is:
For each material, a reference to the data for each material is given
After a line with @ , the ELF data follows in lines with the following meaning

1. Excitation parameters ac, bc to model core excitations (see Penn, J. Elec. Spectr., 9(1976)29).
When ac = 0.001 and bc = -2: no data was available. 

2. Energy gap (eV)

3. Refractive Index

in the next lines, are the parameters for the oscillators: one line for each oscillator

4. energy position (eV), intensity (eV^2), width (eV), alpha
5.
6.
.
.

Examples of data files that can be directly read by QUEELS for Au and Si are seen in the files ELF_Au.txt and ELF_Si.txt respectively.