ENERGY SWITCHING APPROACH TO POTENTIAL SURFACES .2. 2-VALUED FUNCTIONFOR THE WATER MOLECULE

A recently proposed energy switching scheme is used to improve the two -valued many-body expansion potential energy surface of Murrell, Carte r, Mills, and Guest [Mol. Phys. 42, 605 (1981)] for H2O by merging it with the spectroscopically accurate polynomial-type form of Polyanski, Jensen, and Tennyson [J. Chem. Phys. 105, 6490 (1996)]. An attempt is also made to improve its long range forces, and Coulombic behavior at the collapsed molecular limits. The resulting ES two-valued surface h as almost spectroscopic accuracy up to 13 650 cm(-1), and like the ori ginal many-body expansion form may be used for studies of reaction dyn amics: A brief analysis of the Sigma-II locus of conical intersection is also presented. (C) 1997 American Institute of Physics.