Predicting Energetics of Supramolecular Systems Using the XDM Dispersion Model

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate modeling of large supramolecular systems is crucial for understanding non-covalent interactions.
• Dispersion forces significantly influence binding energies in these systems.
• Existing density functional theory (DFT) methods struggle to accurately capture these dispersion effects.

Purpose of the Study:

• To evaluate the efficacy of the exchange-hole dipole moment (XDM) model for dispersion in large supramolecular systems.
• To benchmark XDM-corrected functionals against experimental and Quantum Monte Carlo (QMC) data.
• To identify the most accurate and efficient DFT method for describing dispersion-bound host-guest complexes.

Main Methods:

• Benchmarking of several XDM-corrected DFT functionals using the S12L dataset.
• Comparison of results with experimental and QMC reference data.
• Assessment of the performance of PBE-XDM with the pc-2-spd basis set.

Main Results:

• PBE-XDM/pc-2-spd achieved excellent accuracy (MAE = 1.5 kcal/mol), surpassing experimental/QMC deviations.
• Compared to QMC, PBE-XDM/pc-2-spd (MAE = 1.2 kcal/mol) outperformed all other tested dispersion-corrected DFT methods.
• The dipole-quadrupole (C8) and quadrupole-quadrupole (C10) terms in XDM are vital for accurate dimer descriptions.

Conclusions:

• The PBE-XDM functional, combined with the pc-2-spd basis set, is highly effective for large supramolecular systems.
• This method provides accurate binding energies close to the complete basis-set limit without counterpoise corrections.
• While PBE-XDM excels, other XDM-corrected functionals show limitations for large systems, with errors scaling with dispersion contributions.