A water dimer potential based on a b i n i t i o calculations using Morokuma component analyses

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Abstract
We present a new water dimer potential. It is based on carrying out Morokuma component analyses at the ab initio level on 229 water dimer geometries and fitting the energy components to analytical functional forms. To these are then added a dispersion contribution, based on the analytical dispersion energy expression of Douketis et al. (Ref. 1). This potential gives a satisfactory description of the water dimer, with minimum R(O ⋅ ⋅ ⋅ O)=2.96 Å, ΔE=−5.2 kcal/mol, and minimum energy θ angle between H‐bond donor and acceptor axis of 55°, in good agreement with experimental values of 2.98±0.04 Å, −5.4±0.2 kcal/mol, and 60±10°, respectively. The second virial coefficient B is also calculated in reasonable agreement with experiment, e.g., at 423 K, B (calculated) =−352, compared to B (experimental)=−332 cc/mol.