Accurate molecular van der Waals interactions from ground-state electron density and free-atom reference data

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Accurate calculation of van der Waals (vdW) interactions is crucial for understanding molecular and material properties.
• Traditional methods often rely on empirical parameters or computationally expensive approaches.
• Mean-field electronic structure calculations provide a foundation but often lack accurate long-range vdW descriptions.

Purpose of the Study:

• To introduce a parameter-free method for accurately determining long-range vdW interactions.
• To enable accurate vdW interaction calculations directly from mean-field electronic structure data.
• To improve the predictive power of computational chemistry for systems dominated by vdW forces.

Main Methods:

• Summation of interatomic C6 coefficients derived from the electron density of molecules and solids.
• Utilizing accurate reference data for free atoms to determine atomic C6 values.
• Developing a method independent of the specific exchange-correlation functional used in calculations.

Main Results:

• Achieved a mean absolute error of 5.5% in C6 coefficients compared to experimental values across 1225 intermolecular pairs.
• Demonstrated that effective atomic C6 coefficients are sensitive to the atom's bonding environment within a molecule.
• Provided analysis of van der Waals radii and damping functions for C6R(-6) corrections in density-functional theory.

Conclusions:

• The presented parameter-free method offers an accurate and general approach for calculating long-range vdW interactions.
• The strong dependence of C6 coefficients on the bonding environment highlights the need for context-aware calculations.
• This work provides a robust tool for improving density-functional theory calculations with accurate vdW corrections.