The Common Concept of Anticooperativity Among Molecules Is Fundamentally Flawed, Based on Novel and Unified Molecular-Wide and Electron Density (MOWeD) Concept of Chemical Bonding.

A non-linear (non-additive) increase in stability of hexamers follows an increase in the total number of (i) (a double proton acceptor) plus (a double proton donor) waters commonly linked with anticooperativity and (ii) the total number of intermolecularly delocalized electrons () in the 3D space occupied by a hexamer. Subsequently, we obtained nearly a perfect linear correlation between increase in the cluster stability and . Individual water molecules that act as either or (i) delocalize the largest number of electrons throughout a cluster; (ii) are involved in the strongest attractive, hence energy-stabilizing intermolecular interaction with the remaining five waters; (iii) have the most significant quantum component of the intermolecular interaction energy and (iv) relative to six non-interacting water molecules, stabilize a hexamer the most, as quantified by a purposely derived -FAMSEC energy term. Clearly, the approach used in the unified, molecular-wide and electron density (MOWeD)-based concept of chemical bonding contradicts the commonly accepted view that and water molecules are involved in anticooperativity in 3D water hexamers. Consequently, we propose here a general definition of cooperativity that should be applicable to any -membered molecular cluster, namely