Electronic correlation contribution to the three‐body potentials for water trimers

A number of trimers of water molecules have been computed with an extended basis set in the Hartree–Fock and in the direct CI approximations. It has been verified that the three‐body interaction energy can be calculated within the Hartree–Fock method. Therefore, the correlation corrections to the Hartree–Fock level are essentially additive and do not contribute significantly to three‐body effects.