Ionization potentials within semiempirical antisymmetrized product of strictly localized geminals approach

The APSLG-MINDO/3 method is evolved to reproduce the vertical ionization po tentials for organic molecules. Two different schemes-one allowing for adju stment of the local electronic structure to the hole in each configuration and another one with a fixed local electronic structure are developed and i mplemented. These methods are applied to a series of normal hydrocarbons. T he possibility of localization of a hole in the polyethylene cation is disc ussed. Vertical ionization potentials are also obtained for a set of organi c molecules with heteroatoms. Their values together with degeneracy of ioni zed states are compared with the data of photoelectron spectroscopy. (C) 20 01 John Wiley & Sons, Inc.