J. Zuniga et al., Optimal generalized internal vibrational coordinates and potential energy surface for the ground electronic state of SO2, J CHEM PHYS, 115(1), 2001, pp. 139-148
An optimization of generalized internal vibrational coordinates for the ele
ctronic ground state of the SO2 molecule is carried out. These coordinates
are given by the magnitudes and the angle formed by two vectors expressed a
s linear combinations of the internal valence vectors, and depend on two ex
ternal parameters which can be optimized so as to reduce the vibrational co
upling of the molecule as much as possible. The optimal values of the param
eters are found by minimizing a set of unconverged vibrational energies whi
ch are computed variationally using a small basis function set. It is shown
that the optimal internal coordinates obtained for SO2 are superior to bot
h valence and Radau coordinates, as well as to a set of normal coordinates
previously derived by proper rotation of the Jacobi S-O-2 coordinates. Thes
e optimal internal coordinates are then applied to calculate the vibrationa
l energies of the molecule using an ab initio force field expressed as a Mo
rse-cosine expansion, and then to refine it by nonlinear least-squares fitt
ing to the observed vibrational frequencies. (C) 2001 American Institute of
Physics.