Ab initiocalculation for the fundamental frequencies of H2O

Abstract
The question of the best method to determine frequencies of triatomic molecules by entirely ab initio methods is discussed, with reference to H2O. MCSCF-CI calculations are reported at selected geometries, and have been used to generate a potential surface from which the vibrational energies are calculated by a variational method. The calculated fundamental frequencies are in error by 28 cm-1 (bend), and 10 cm-1 and 4 cm-1 (symmetric and asymmetric stretch).