  A new formalism to calculate the transmission coefficient t of electrons from
a material L into the same material L through a barrier B is presented. The
barrier B is arbitrary and can be metallic, semiconducting or insulating. The
important feature of this formalism is that it starts from the electronic
structure of a periodic L/B superlattice. The electronic stucture of such a
superlattice is calculated selfconsistently within a Screened
Korringa-Kohn-Rostoker method. The capability of the new method is demonstrated
by means of a free electron model. First results for the transmission of Cu
electrons through a Co layer are presented.
