INFLUENCE OF FLUORINE DESORPTION ON ELECTRONIC-STRUCTURE OF CAF2-LCAOSLAB CALCULATIONS

The electronic structure of a 12 molecular layer slab of CaF2 with flu orine ions desorbed from the (111) surface was calculated using the LC AO method. During experimental investigations this surface very often undergoes either electron beam bombardment or uv radiation illuminatio n. It has been already proved that such a treatment leads to fluorine desorption. Using the standard LCAO procedure with semiempirical param eters, proved to reproduce well the electronic structure of a bulk cry stal we obtained an additional band of states inside the energy gap, w ith valence and conduction bands almost unchanged. The position on the energy scale and the width of this new band correspond well with the electron energy loss spectra (EELS) for CaF2.