# 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

## TL;DR

This paper challenges the traditional understanding of anticooperativity in water clusters by introducing a new concept based on electron delocalization and molecular stability.

## Contribution

The paper introduces the MOWeD concept, which redefines cooperativity through intermolecular electron delocalization.

## Key findings

- Hexamer stability increases with the number of intermolecularly delocalized electrons.
- aad and add water molecules stabilize clusters more than previously thought.
- A new energy term, mol-FAMSEC, quantifies the stabilization effect of these molecules.

## Abstract

A non-linear (non-additive) increase in stability of hexamers follows an increase in the total number of (i) aad (a double proton acceptor) plus add (a double proton donor) waters commonly linked with anticooperativity and (ii) the total number of intermolecularly delocalized electrons (intermolNdeloc) in the 3D space occupied by a hexamer. Subsequently, we obtained nearly a perfect linear correlation between increase in the cluster stability and intermolNdeloc. Individual water molecules that act as either aad or add (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 mol-FAMSEC energy term. Clearly, the all-body approach used in the unified, molecular-wide and electron density (MOWeD)-based concept of chemical bonding contradicts the commonly accepted view that aad and add 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 n-membered molecular cluster, namely the quantifiable, classical physics- and quantum-based cooperativity phenomenon is synonymous with the intermolecular all-body delocalization of electrons, leading to the increase in stability of individual molecules on an n-membered cluster formation.