Hg. Kjaergaard et Br. Henry, AB-INITIO CALCULATION OF DIPOLE-MOMENT FUNCTIONS - APPLICATION TO VIBRATIONAL BAND INTENSITIES OF H2O, Molecular physics, 83(6), 1994, pp. 1099-1116
The dipole moment function of H2O has been calculated at different lev
els of ab initio theory. The ab initio calculations range from Hartree
-Fock to perturbative, limited configuration interaction, and coupled
cluster methods, and cover a wide range of standard basis sets. The di
pole moment function is taken as a series expansion in the bond coordi
nates, with expansion coefficients found from the ab initio results. T
hese different dipole moment functions are used to calculate fundament
al and overtone vibrational band intensities of H2O. A simple three-di
mensional harmonically coupled anharmonic oscillator local mode descri
ption is employed to obtain the vibrational energies and wavefunctions
. The results indicate that useful vibrational band intensities can be
obtained from a limited ab initio approach. Fundamental intensities a
re more sensitive to electron correlation than overtone intensities. T
his provides an insight into the quality of dipole moment function nec
essary to calculate reasonable values for fundamental and overtone int
ensities, an insight that is important for studies with larger molecul
es where the highest levels of theory are not computationally feasible
.