Three-Body Dispersion Corrections to the Spherical Atom Model: The PFD-3B Density Functional.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate prediction of molecular energies is crucial for understanding chemical reactions and properties.
• Existing isotropic spherical atom models have limitations in capturing complex interactions.
• Three-body dispersion interactions play a significant role in molecular systems.

Purpose of the Study:

• To develop and evaluate a new density functional, PFD-3B, that enhances accuracy in energy calculations.
• To assess the performance of PFD-3B against benchmark datasets and existing methods.
• To investigate the functional's suitability for geometry optimization and vibrational frequency calculations.

Main Methods:

• Combining isotropic spherical atom models with anisotropic three-body dispersion interactions.
• Developing the PFD-3B density functional.
• Testing the functional against the S22 and S22 × 5 benchmark datasets.
• Comparing PFD-3B results with coupled cluster with single, double, and perturbative triple excitations (CCSD(T))/complete basis set (CBS) benchmark energies.

Main Results:

• PFD-3B reduces the mean absolute deviation (MAD) from 0.78 to 0.19 kcal/mol for the S22 test set.
• High accuracy is maintained across a wide range of molecular geometries.
• PFD-3B outperforms previously applied functionals on the S22 × 5 dataset.
• Excellent agreement with benchmark values for bond lengths (R_e), dissociation energies (D_e), and vibrational frequencies (ω_e) was achieved for both small and larger molecules.

Conclusions:

• The PFD-3B density functional represents a significant advancement in computational chemistry accuracy.
• Its ability to accurately model dispersion interactions makes it highly suitable for predicting molecular properties.
• PFD-3B is a promising tool for geometry optimization and zero-point energy calculations due to its high accuracy and efficiency.