The R(-7) Dispersion Interaction in the General Effective Fragment Potential Method

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Intermolecular Forces

Background:

• The dispersion expansion describes van der Waals interactions.
• Accurate modeling of these forces is crucial for predicting molecular behavior.

Purpose of the Study:

• To develop and formulate the R(-7) dispersion term (E7) within the effective fragment potential (EFP2) framework.
• To investigate the properties and applicability of the E7 term, particularly its orientation dependence.

Main Methods:

• Utilized the general effective fragment potential (EFP2) method.
• Employed dynamic anisotropic Cartesian polarizability tensors over the imaginary frequency range.
• Incorporated an origin transformation for localized molecular orbital (LMO) dipole-quadrupole polarizability calculations.
• Extended overlap-based and Tang-Toennies damping functions for the R(-7) interaction.

Main Results:

• Formulated the E7 term using total molecular polarizability and LMO contributions.
• Demonstrated that the R(-7) dispersion interaction is highly orientation-dependent, exhibiting both attractive and repulsive characteristics.
• Showcased the significance of the E7 term in systems where rotational averaging is not applicable, such as molecular solids.

Conclusions:

• The developed R(-7) dispersion term (E7) provides a more nuanced understanding of intermolecular interactions.
• The orientation dependence of E7 is critical for accurately describing interactions in non-rotating molecular systems.
• This formulation enhances the predictive power of the EFP2 method for complex molecular assemblies.