A post-Hartree-Fock model of intermolecular interactions

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Modeling

Background:

• Intermolecular interactions are crucial in chemistry but challenging to model computationally.
• Standard methods like Hartree-Fock and density-functional theory lack accurate physics for dispersion forces.
• Current dispersion corrections, such as pairwise C6R6 terms, rely on empirical coefficients.

Purpose of the Study:

• To develop a post-Hartree-Fock model for accurate calculation of intermolecular interactions.
• To generate C6 dispersion coefficients from the instantaneous dipole moment of the exchange hole.
• To introduce a model with a single, universal empirical parameter for dispersion energy at short interatomic distances.

Main Methods:

• A post-Hartree-Fock approach utilizing occupied orbitals only.
• Generation of C6 dispersion coefficients based on the exchange hole's instantaneous dipole moment.
• Inclusion of one universal empirical parameter to regularize dispersion energy.

Main Results:

• The model was validated on 178 intermolecular pairs for isotropic C6 coefficients.
• Calculations of geometries and binding energies for 20 intermolecular complexes showed excellent agreement.
• The model successfully accounts for dispersion, dipole-induced dipole, dipole-dipole, and hydrogen-bonding interactions.

Conclusions:

• The presented model accurately captures intermolecular interactions, particularly dispersion forces.
• It offers a significant improvement over standard computational chemistry methods.
• The model's reliance on occupied orbitals and a single parameter makes it efficient and broadly applicable.