Rationalizing Aggregate Structures with Orbital Contributions to the Exchange-Repulsion Energy.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular interactions

Background:

• Repulsive interactions are critical in non-covalently bonded systems.
• Existing electrostatic models often fail to accurately describe these interactions.
• Understanding these forces is key to predicting molecular aggregate structures.

Purpose of the Study:

• To propose a molecular orbital-based model for exchange repulsion.
• To elucidate the role of repulsive forces in the structure of molecular aggregates.
• To explain limitations of current electrostatic models.

Main Methods:

• Development of a molecular orbital-based model for exchange repulsion.
• Analysis of the nodal structure of occupied orbitals.
• Application to model systems like Cl2-He, benzene-benzene, and benzene-hexafluorobenzene aggregates.

Main Results:

• Energetically favorable aggregate structures often show reduced exchange repulsion.
• This reduction is linked to the nodal properties of specific occupied molecular orbitals.
• The proposed model successfully explains features of intermolecular potentials where electrostatic models fail.

Conclusions:

• Repulsive exchange interactions are fundamental to understanding non-covalent systems.
• The molecular orbital-based model provides a more accurate description of intermolecular potentials.
• This approach offers new avenues for predicting and designing molecular assemblies.