Orbitalparameter aus Elektronendichten

Models for describing substances, their properties and reactions are a central
point in chemistry. It's helpfull to describe complex relations by simple models
and concepts even if they describe the observable reality only approximately.
Examples are the quite successfull concepts of formal charges or Bohr's atomic
model. The essential point is a deeper understanding of what's going on physically and to be able to make reasonable predictions for similar problems.
The complex reality of this work is the electron density of a molecule or a crystal which can be generated by x-ray diffraction, the simple model is the wellknown atomic orbital concept with orbital parameters (occupation numbers and orientations of the valence orbitals). The electron density is complicated among others, because nature does not offer a definite way to partition the electron density into atom and orbital contributions. The aim of this work is to decompose the electron density in terms of orbital parameters (see above). Thereby one can describe the electron density (and therefore many properties) of this substance and second there results a deeper understanding of how the atoms are bonded in this system.
A program modul for an existing x-ray program package (XD of the IUCr) has been written in order to extract orbital parameters from an experimental (or theoretical) data set, and then it was applied to two exemplary substances: oxalic acid dihydrate and cobalt sulfite dihemihydrat.