Challenging Dogmas: Hydrogen Bond Revisited

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Molecular Interactions

Background:

• Understanding hydrogen bond directionality is crucial for molecular recognition and condensed-phase properties.
• Water dimer presents a fundamental model for studying hydrogen bonding interactions.

Purpose of the Study:

• To elucidate the underlying energetic contributions governing hydrogen bond directionality in the water dimer.
• To analyze the interplay of electrostatic, exchange-repulsion, dispersion, and induction forces.

Main Methods:

• Symmetry-Adapted Intermolecular Perturbation Theory (SAIP)
• Decomposition of intermolecular interaction energy into four components.

Main Results:

• The linear configuration of the water dimer is preferred due to a complex interplay of all four energy components.
• Electrostatic and exchange-repulsion forces largely cancel each other near the equilibrium geometry.
• Induction and dispersion forces play a significant role in stabilizing the dimer.

Conclusions:

• Hydrogen bond directionality in water dimers is not dominated by a single force but by a delicate balance.
• SAIP provides a robust framework for dissecting intermolecular forces and understanding molecular arrangements.