Ab initio calculations of the Ar-ethane intermolecular potential energy surface using bond function basis sets.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Understanding intermolecular forces is crucial for predicting molecular behavior.
• Accurate potential energy surfaces (PES) are essential for molecular simulations and spectroscopy.
• Previous studies may lack the precision needed for detailed Ar-ethane interactions.

Purpose of the Study:

• To compute a highly accurate intermolecular potential energy surface (PES) for the argon-ethane system.
• To investigate the impact of bond functions on the convergence and accuracy of the PES.
• To compare the performance of different theoretical methods, including MP2 and CCSD(T).

Main Methods:

• Ab initio calculations using second-order Møller-Plesset perturbation (MP2) and coupled-cluster with single, double, and noniterative triple configurations (CCSD(T)) theories.
• Employment of augmented correlation-consistent basis sets with and without bond functions (bf1, bf2).
• Analysis of the PES for minimum energy configurations and potential anisotropy.

Main Results:

• A global minimum near a T-shaped configuration (well depth 0.611 kcal mol⁻¹) and a secondary minimum at a collinear configuration (well depth 0.456 kcal mol⁻¹) were identified.
• Augmented correlation-consistent basis sets augmented with bond functions demonstrated improved convergence and accuracy.
• The MP2 method was found to be inadequate, yielding overestimated well depths and poor potential anisotropy.

Conclusions:

• Bond functions significantly enhance the accuracy of ab initio calculations for intermolecular PES.
• CCSD(T) calculations with augmented basis sets and bond functions provide reliable Ar-ethane interaction potentials.
• The study highlights the limitations of the MP2 method for this system and the benefits of advanced computational strategies.