Improved ELNES interpretation

The fine structure in ionization edges (ELNES, Electron Energy Loss Near Edge Structures) mirrors the density of unoccupied states above the Fermi energy. It is thus an important source of information on the electronic structure of materials. A better understanding of the ELNES will lead to a wide range of applications related to the macroscopic properties of materials. In the present project, it is planned to improve the understanding of ELNES by comparing experiments with two kinds of simulations. The simulations will be done with a band-structure method (the WIEN 97 Full Linearized Augmented Plane Waves code) and a multiple scattering method (FEFF8). The first step is to implement the following effects into the codes, which have an influence on the ELNES : angular integration over the scattering vector, non-dipole terms, mixed dynamic form factor, core-hole and lifetime. Experiments and corresponding simulations will be done on a wide range of materials in order to determine which code is better in which case - and why this is so. The different material classes will be: Al and Al2O3 to study the lifetime effect, d-metals to study the core-hole, anisotropic materials (important to test the implementation of the scattering vector dependence) substitutional alloys (CuNi, TiAl) and metals that build ordered phases, perovskites and interfaces. This work will be done in collaboration with two other research institutions the Laboratoire d`etude des microstructures (LEM)-ONERA and the Laboratoire de Mecanique des Sols, Structures et Materiaux, Ecole Centrale Paris. The LEM will participate in the FEFF development and the study of, TiAl and the ECP will participate in the study of perovskites and anisotropic materials.