Covalent features in the hydrogen bond of a water dimer: molecular orbital analysis

TL;DR

This study uses advanced quantum chemical methods to demonstrate the covalent-like nature of hydrogen bonds in water dimers, revealing molecular orbitals that cross the hydrogen bond and highlighting the importance of induction effects.

Contribution

It provides the first molecular orbital analysis showing covalent-like features in water hydrogen bonds, combining DFT and post-Hartree-Fock methods.

Findings

Identification of two bonding molecular orbitals crossing the hydrogen bond

Significant induction contribution to hydrogen bonding

Enhanced understanding of water's intermolecular interactions

Abstract

The covalent-like characteristics of hydrogen bonds offer a new perspective on intermolecular interactions. Here, using density functional theory and post-Hartree-Fock methods, we reveal that there are two bonding molecular orbitals (MOs) crossing the O and H atoms of the hydrogen-bond in water dimer. Energy decomposition analysis also shows a non-negligible contribution of the induction term. These results illustrate the covalent-like character of the hydrogen bond between water molecules, which contributes to the essential understanding of ice, liquid water, related materials, and life sciences.