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

Document Type : Research Paper

Abstract

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

Keywords

• FSGO
• MDFSGO
• Orbital
• Lone pair
• Gaussian
• Dipole moment

---