Formaldehyde Molecule in a Gaussian Basis. One-Electron Properties

Numerous one‐electron properties of the formaldehyde molecule have been calculated using Hartree–Fock–Roothaan wavefunctions obtained from three different basis sets: an unoptimized minimum basis set of Slater orbitals, a (73 / 2) Gaussian basis set, and a (95 / 3) Gaussian basis set. Comparison of the calculated and experimental values is made whenever possible, the agreement in most cases being satisfactory. Use of the more flexible Gaussian wavefunctions results in significant improvements in many of the properties. Consideration of the atoms shows that no appreciable error arises from the use of Gaussian orbitals as expansion functions for the solution of the Hartree–Fock equations. Even though the best wavefunction is near the $\mathrm{(sp)}$ limit, some properties (such as the dipole moment and forces) are still inadequately described. Such a basis set is just not sufficient to describe the polarizations of the atoms caused by molecular formation. Inclusion of $d$ orbitals in the basis set should substantially improve such properties.