RMCS–CI potential surface for H2O→OH+H

Abstract

A potential surface is reported for H2O at a fixed bond angle of 105°. The surface covers an extended range, including the dissociation channels OH(2Π)+H(2S) and O(3P)+2H(2S). Using a double-zeta basis set and multireference CI technique, followed by a fitting procedure using rotated Morse curves, the following results were obtained: H2O(1A1)→OH(2Π)+H(2S), ΔE=4.50 eV (expt. 5.47); H2O(1A1)→O(3P)+2H(2S), ΔE=8.03 eV (expt.10.08). A double-zeta + polarization basis set leads to improved results (5.18 and 9.44 eV). The shape of the surface is well described by rotated Morse curves. A simple scaling procedure brings the computed surface into close coincidence (within ∼0.2 eV) with a surface based on an experimental force field. The scaled RMCS–CI approach may be useful for other triatomic systems to provide an accurate surface at a reasonable cost.