Magnetism

Abstract

In our previous discussions of the electronic structure of materials we have assumed the one-electron approximation. The energy levels and the bandstructure were calculated for an electron in an effective potential consisting of the potential of the ion cores and an average potential due to the other electrons. Within this model quite acceptable bandstructures can be calculated. However, another aspect of the one-electron model is more important than the qualitative agreement with experiment and the (in principle) simple calculational method: Within the one-electron model it is also possible to understand conceptually the excited states of the electronic system, resulting for example from the interaction with photons and other particles or from thermal excitation.