Weak binding between two aromatic rings: feeling the van der Waals attraction by quantum Monte Carlo methods

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Chemical Physics

Background:

• Understanding intermolecular forces is crucial for predicting molecular behavior.
• The weak interaction between aromatic systems like benzene is of significant interest.
• Accurate computational methods are needed to describe these subtle interactions.

Purpose of the Study:

• To systematically investigate the weak chemical bond between two benzene molecules.
• To accurately determine the binding energy and preferred geometry of the benzene dimer.
• To validate computational methods against experimental findings.

Main Methods:

• Utilized pseudopotentials for core electrons and a resonating valence bond (RVB) wave function.
• Employed an improved stochastic reconfiguration technique for wave function optimization.
• Applied lattice regularized diffusion Monte Carlo (LRDMC) for highly accurate energy calculations.

Main Results:

• Achieved a highly accurate description of the benzene dimer using a combination of RVB and LRDMC.
• Found the parallel displaced geometry to have significantly deeper energy dispersion than face-to-face.
• Calculated a weak binding energy of approximately 2 kcal/mol for the parallel displaced configuration.

Conclusions:

• The study provides accurate binding energies for the benzene dimer, consistent with experimental data.
• The parallel displaced geometry is energetically favored over the face-to-face configuration.
• The employed computational approach offers a robust method for studying weak intermolecular interactions.