pi-SCF-molecular mechanics PIMM: formulation, parameters, applications

A pi-SCF/Molecular Mechanics method (PIMM) for the calculation of heats of formation, molecular geometries and charge density distributions of organic molecules is described. The method combines a pi-SCF molecular orbital calculation and the sigma-charge evaluation procedure PEOE of Marsilli and Gasteiger with molecular mechanics. The formulas and parameters used are given. A series of results for small molecules is presented and compared with experimental data.