WHAT IS THE GLOBAL MINIMUM ENERGY STRUCTURE OF THE WATER HEXAMER - THE IMPORTANCE OF NONADDITIVE INTERACTIONS

The global minimum energy structures of the water hexamer predicted by widely used analytic water potentials are very different from each ot her, while the cyclic hexamer does not appear to be a low-lying energy structure. However, high levels of ab initio calculation predict that a number of low-lying energy conformers including the cyclic conforme r are almost all isoenergetic due to the balance of two-body and nonad ditive interactions. For modeling of water potentials, we suggest that the binding energy of the dimer be between - 5.0 and -4.7 kcal (mol d imer)(-1), while the three-body corrections be taken into account to a large extent.