Bonding analysis of water clusters using quasi-atomic orbitals

Area of Science:

• Computational Chemistry
• Physical Chemistry
• Molecular Dynamics

Background:

• Hydrogen bonding in water clusters is fundamental to many chemical and biological processes.
• Understanding the evolution of hydrogen bond strength with cluster size is crucial.
• Previous studies have explored water clusters, but a detailed analysis of hydrogen bond dynamics using advanced methods is needed.

Purpose of the Study:

• To investigate the nature and strength of hydrogen bonds in small water clusters (dimer to hexamer).
• To analyze various water cluster conformers, including cyclic, bag, boat, book, prism, and cage structures.
• To elucidate the three-center bonding characteristics of hydrogen bonds in these systems.

Main Methods:

• Application of the quasi-atomic orbital (QUAO) bonding analysis method.
• Utilizing kinetic bond orders as a quantitative metric for hydrogen bond strength.
• Systematic examination of water clusters ranging from the dimer to the hexamer.

Main Results:

• Demonstrated strengthening of hydrogen bonds in simple cyclic water clusters as the number of water molecules increases.
• Observed variations in hydrogen bond strength for complex hexamer isomers, dependent on double donor/acceptor presence.
• The QUAO analysis confirmed the three-center bonding nature inherent in water cluster hydrogen bonds.

Conclusions:

• The quasi-atomic orbital (QUAO) bonding analysis provides valuable insights into hydrogen bond evolution in water clusters.
• Hydrogen bond strength is size-dependent in simple cyclic clusters but conformation-dependent in more complex structures.
• The study confirms the three-center bonding model for hydrogen bonds within water clusters.