Electrostatic interactions and hydrogen bond in clusters. Theoretical approach

Some semi-empirical methods for calculation of the leading terms o f the intermolecular potential are reviewed. In particular, the semi-empirical approach based on the exchange perturbation theory is closely inspected. The balance between the electrostatic interaction and the repulsion-dispersion term is specially discussed. The difficulties remaining in the case of a strong hydrogen bond, i.e, the calculation of repulsion and polarization terms are analysed. Many examples are given all along the overall discussion.