Smooth Dispersion Is Physically Appropriate: Assessing and Amending the D4 Dispersion Model

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Dispersion corrections are crucial for accurate density functional theory (DFT) predictions.
• The D4 scheme is widely used for its efficiency and accuracy.
• However, the D4 model can introduce unphysical features into potential energy surfaces.

Purpose of the Study:

• To investigate anomalies in the D4 dispersion correction scheme.
• To propose and evaluate new methods for smoother dispersion energy calculations.
• To address unphysical local minima and stationary points caused by the D4 model.

Main Methods:

• Analysis of D4 scheme anomalies.
• Development of D4S (smoother Gaussian weighting) and D4SL (soft linear interpolation) models.
• Assessment of accuracy and smoothness of the new models compared to D4.

Main Results:

• Anomalies, including unphysical curvature and bumps, are common in the D4 model.
• Instances of unphysical local minima and stationary points were identified with D4.
• The proposed D4S and D4SL methods generally eliminate artificial extremum points.
• The new methods maintain the accuracy of the original D4 scheme.

Conclusions:

• The D4 scheme can produce unphysical artifacts in potential energy surfaces.
• D4S and D4SL provide effective solutions for achieving smoother dispersion energy calculations.
• These improved models enhance the reliability of DFT for various chemical and material applications.