Study of lone pair description in molecules by the modified delocalized floating spherical Gaussian orbital method.

This research has been carried out to study and find a rather general description for a lone pairorbital in molecules. Since the orbital parameters must be manageable in advance, and correctgeometry of the molecule (bond lengths) is depend on the appropriate lone pair description; theFSGO method including optimization has been used to obtain orbital parameters and energy. Theproposed models for lone pair description have been tested by two molecules: HF and NH.29models for HF and 23 models for NH have been used to obtain simultaneously correct bond lengthand dipole momentum. We show that contribution of lone pair electrons in binding givessatisfactory results. An approach which we called “Modified Delocalized Floating sphericalGaussian orbital (MDFSGO)” method was performed for these molecules. The linear combinationof p-type and s-type orbital are tested. They can predict only correct bond length or dipolemomentum, but the contribution of lone pair electrons in binding can predict rather satisfactoryresults for both bond length and dipole momentum. By using this method, the error of dipolemoment and bond length decrease from 229.75% to %9.72 and from 27.28% to 4.03% in HFmolecule. For NH, the error of dipole momentum changes from 256.45% to 8.023% and for bondlength from 32.84% to 1.92%.