Binding in the Ar-I(2)(X(1)Σ(g)(+)) complex: a challenge for theory and experiment

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Spectroscopy

Background:

• Understanding intermolecular forces in van der Waals complexes like Argon-Iodine (Ar-I2) is crucial for molecular dynamics and spectroscopy.
• Accurate potential energy surfaces (PES) are essential for predicting complex properties, but experimental data can sometimes be limited or ambiguous.

Purpose of the Study:

• To perform high-level ab initio calculations for Ar-I2 to determine its potential energy surface (PES).
• To compare calculated dissociation energies (D0) with existing experimental data.
• To refine theoretical models for van der Waals complexes using a Density-Independent Many-Body (DIM) correction.

Main Methods:

• High-level ab initio calculations were employed to generate the potential energy surface for Ar-I2.
• Calculated bond dissociation energies (D0) for linear (L) and T-shaped (T) conformers were analyzed.
• A Density-Independent Many-Body (DIM) based correction was applied and tested on Ar-Cl2 before application to Ar-I2.

Main Results:

• Direct ab initio calculations yielded D0 values significantly higher than recent experimental data for both Ar-I2 conformers.
• The DIM-based correction successfully predicted D0 values for Ar-I2 (L: ~250±8 cm⁻¹, T: ~242±11 cm⁻¹).
• The corrected values align well with earlier experimental results, indicating improved accuracy.

Conclusions:

• Initial ab initio calculations for Ar-I2 may overestimate bond dissociation energies compared to some experimental findings.
• The DIM-based correction provides a more accurate theoretical prediction of Ar-I2 dissociation energies.
• This study highlights the importance of refining theoretical models to achieve better agreement with experimental observations in van der Waals complexes.