THE MEASUREMENT AND USE OF TOPOLOGICAL FEATURES OF THE EXPERIMENTAL ELECTRON DENSITY V.G.Tsirelson, Mendeleev University of Chemical Technology, Moscow, Russia

The quantum topological theory, developed by Bader, allows to analyze the chemical bond, intermolecular interactions and properties of molecules and crystals in terms of the features of the electron density which can be measured experimentally. The experimental electron density, however, is dynamic and suffers from both statistical uncertainty of the measurement results and Fourier series truncation error. When the multipole modelling of the electron density is used, the model error can be significant as well. All these circumstances influence the topological characteristics obtained.

There are three methods of calculation of the topological features of the experimental electron density. One of them is based on finite-difference calculation of the derivatives of the electron density presented in the Fourier series form. The second method uses combination of promolecule and deformation electron densities. The third method is based on model description of the electron density. The advantages and shortages of each of these approaches are discussed in this talk. The results of the experimental topological studies of inorganic, organic and organo-element compounds show that semi-quantitative agreement with theoretical data is observed as a rule.

The use of topological features of the experimental electron density for study of non-standard cases of the chemical bond, long-range interactions in solids as well as for the ground of some crystal chemical notions are discussed.