FLOATING SPHERICAL GAUSSIAN ORBITAL MODEL OF MOLECULAR STRUCTURE .6. DOUBLE-GAUSSIAN MODIFICATION

The floating spherical gaussian orbital model is modified to improve molecular energies and geometry by using a linear combination of two concentric spherical Gaussian orbitals (a double Gaussian) as the localized orbital. The double-Gaussian model was applied to hydrogen, the first-row atom hydrides, and a series of hydrocarbons. Bond lengths are predicted within 5.8% and bond angles within 6.6% for all the cases investigated. Molecular energies are generally 96% of Hartree-Fock values, and bond angles are improved.