r²SCAN-D4: Dispersion corrected meta-generalized gradient approximation for general chemical applications.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Density functional theory (DFT) is a cornerstone of modern computational chemistry.
• Accurate description of electron correlation and dispersion forces remains a challenge.
• Existing functionals often involve trade-offs between accuracy and computational cost.

Purpose of the Study:

• To develop a new density functional approximation (r²SCAN-D4) that balances accuracy and computational efficiency.
• To evaluate the performance of r²SCAN-D4 across a wide range of chemical systems and properties.
• To assess the numerical robustness of the new functional in practical applications.

Main Methods:

• Combining a regularized variant of the strongly constrained and appropriately normed (r²SCAN) semilocal density functional with a semi-classical London dispersion correction (D4).
• Benchmarking against established datasets for molecular geometries, thermochemistry (main group and organometallic), and non-covalent interactions.
• Evaluating performance on supramolecular complexes, molecular crystals, and metal-organic reactions.

Main Results:

• r²SCAN-D4 achieves accuracy comparable to hybrid functionals with the speed of generalized gradient approximations.
• Exceptional performance on the GMTKN55 database (WTMAD2 of 7.5 kcal/mol) and metal-organic reactions (MAD of 3.3 kcal/mol).
• Accurate prediction of bond lengths (0.8% error) and lattice energies (<1 kcal/mol error) for molecular crystals.

Conclusions:

• r²SCAN-D4 represents a significant advancement in density functional approximations for general chemical applications.
• The functional demonstrates broad applicability and numerical robustness for organic, organometallic, and condensed-phase systems.
• This method offers a computationally efficient yet highly accurate approach for diverse chemical modeling tasks.