Abstract：

The concept of valence and core electrons is familiar to every chemist and underlying, for example, the ordering of the elements in the periodictable. For many qualitative considerations the chemistry of an element is only determined by its valence electrons, which actively participate in chemical bonding. The method of effective core potentials (ECP) makes use of these ideas in electronic structure theory calculation. The goals are a considerable reduction of the computational effort by avoiding the costly explicit treatment of the atomic cores in the calculations and at the same time an implicit treatment of the major relativistic effects for the valence electronic system. In this talk, the Stuttgart-cologne type ECP which is pop in heavy element calculation will be introduced and the application in actinide and lathanide chemistry will be discussed.