Theoretical Study of SO2 Molecular Properties

Using two contracted Gaussian functions for each atomic orbital, plus $d$ functions on both sulfur and oxygen to describe molecular charge distortion, a self‐consistent‐field wavefunction was computed for the ${}^1{A}_1$ ground state of SO₂. It is estimated that the calculated SCF energy, − 547.2089 hartree, lies no more than 0.1 hartree above the Hartree–Fock energy for SO₂. An additional calculation without $d$ functions and population analyses indicate that (a) $d$ functions on sulfur are much more important in SO₂ than was the case in previous work on H₂S and (b) in SO₂, $d$ functions on sulfur are much more important than those on oxygen. Calculated molecular properties are in good agreement with available experimental data. Of particular importance is the fact that the calculated elements of the molecular quadrupole moment tensor are 31%, 30%, and 29% greater than those recently determined experimentally by Pochan, Stone, and Flygare. Values of the third moments, octupole moment tensor, diamagnetic shielding tensor, electric field gradient tensor, and ¹⁷O quadrupole coupling constants are predicted. On the basis of ab initio electric field gradients and experimental ³³S quadrupole coupling constants for OCS, H₂S, and SO₂, we deduce nuclear electric quadrupole moments: ${\mathrm{Q(}}^{33}\mathrm{S}\text{)\hspace{0.17em}=\hspace{0.17em}−\hspace{0.17em}0.062}\mathrm{b}$ and ${\mathrm{Q(}}^{35}\mathrm{S}\text{)\hspace{0.17em}=\hspace{0.17em}0.043}\mathrm{b}$ .