Theoretical study of water trimer

Abstract

Geometry optimizations, rearrangement mechanisms, reaction pathways, spectral intensities, and tunneling splittings are reported for the water trimer at various levels of theory. Three of the four pathways which exist for a simple empirical rigid-molecule effective pair potential appear to be quite realistic, as evidenced by ab initio calculations of increasing quality up to DZP basis sets with correlation energy corrections from second-order MOller-Plesset theory. The spectroscopic consequences of the nonrigidity implied by the various rerrangement mechanisms are also considered; the pathways permit the interconversion within two subsets of the 96 permutationally distinct (H 2 O) 3 clusters that arise when only O-H hydrogen bonds, as opposed to chemical bonds, may break