ON THE NATURE OF CRYSTALLINE BONDING - EXTENSION OF STATISTICAL POPULATION ANALYSIS TO 2-DIMENSIONAL AND 3-DIMENSIONAL CRYSTALLINE SYSTEMS

In a previous publication, the so-called statistical population analysis (SPA) has been developed and applied to 1D periodic systems (polymers). The goal; of the present work is to implement the formalism extended to higher dimensional cases and to perform its application to 2D layers (graphite and hexagonal boron nitride), 3D crystals (diamond and cubic boron nitride) and two cases of atomic adsorption- on surface (carbon + graphite; oxygen + graphite), in the framework of the semiempirical MNDO-CO-LCAO State function approach. Rather than attempting to improve the band structures our goal is to give complete detail of the electronic distribution in atoms and bonds by means of population analysis algorithms for the above-mentioned systems. SPA results pert-nit the showing of striking and novel effects on chemical bonding arising from the cooperative contribution of the whole crystalline environment. Different kinds of effective chemisorption bonds are detected for the absorption cases on a surface which is characterized by binding energies of opposite signs. The partitioning scheme of SPA shows that the proposed population analysis is a suitable tool for describing the electronic distribution of isolated and interacting crystalline systems even encouraging its application to the study of more complex situations in which catalysis phenomena are present.