Semiempirical GGA-type density functional constructed with a long-range dispersion correction.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Theoretical Chemistry

Background:

• Accurate description of molecular interactions is crucial in computational chemistry.
• Existing generalized gradient approximation (GGA) functionals often struggle with noncovalent interactions and complex reaction energetics.
• Dispersion forces, particularly at medium to large interatomic distances, are critical for many chemical systems.

Purpose of the Study:

• To introduce and validate a new density functional, B97-D, designed for general chemistry applications.
• To improve the accuracy of density functional theory (DFT) calculations, especially for systems dominated by dispersion forces.
• To provide a robust and efficient computational method for large molecular systems.

Main Methods:

• Development of a new GGA density functional (B97-D) incorporating damped, atom-pairwise dispersion corrections.
• Parameterization of the dispersion correction for elements up to xenon and scaling factors for common functionals (e.g., BLYP, PBE).
• Validation against standard thermochemical benchmark sets, noncovalently bound complexes, molecular geometries, and challenging organometallic reactions.

Main Results:

• B97-D demonstrates high accuracy for thermochemical data, achieving a mean absolute deviation of 3.8 kcal mol(-1) for the G97/2 set.
• Exceptional performance for noncovalently bound systems, reaching near CCSD(T) accuracy for van der Waals complexes.
• Accurate prediction of reaction energetics for notoriously difficult cases, including alkane isomerization, where it correctly predicts energy differences.

Conclusions:

• B97-D is a highly accurate and robust general-purpose GGA functional, particularly effective for systems with significant dispersion interactions.
• The approach of combining short-range DFT with long-range dispersion corrections proves successful for complex chemical problems.
• B97-D is recommended as an efficient quantum chemical method for studying large systems where dispersion forces are important.