r²SCAN-3c: A "Swiss army knife" composite electronic-structure method

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Development of accurate and efficient electronic-structure methods is crucial for chemical research.
• Existing semi-local density-functional theory (DFT) methods often struggle with accuracy or computational cost.
• Meta-generalized-gradient approximations (mGGAs) offer improved performance but can suffer from self-interaction error.

Purpose of the Study:

• To introduce a new composite electronic-structure method, r²SCAN-3c, based on the r²SCAN mGGA functional.
• To evaluate the performance and robustness of r²SCAN-3c across a wide range of chemical applications.
• To compare r²SCAN-3c with existing DFT methods in terms of accuracy and computational efficiency.

Main Methods:

• Construction of the r²SCAN-3c method by combining the r²SCAN functional with a triple-ζ Gaussian basis set.
• Inclusion of refitted D4 and geometrical counter-poise corrections for dispersion and basis set superposition error.
• Comprehensive benchmarking using the GMTKN55 database, non-covalent interactions, organometallic reactions, and adsorption studies.

Main Results:

• r²SCAN-3c demonstrates spectacular performance and robustness across diverse chemical benchmarks.
• The method significantly surpasses its predecessor (B97-3c) in accuracy at a comparable cost.
• r²SCAN-3c achieves top-tier results among semi-local DFT/QZ methods for the GMTKN55 database at a fraction of the cost.
• It outperforms hybrid-DFT/QZ approaches for reaction energies and non-covalent interactions at significantly lower computational expense.
• Self-interaction error, while present, is slightly reduced compared to other (m)GGAs.

Conclusions:

• r²SCAN-3c is a remarkably efficient and robust composite electronic-structure method.
• Its high accuracy and low cost make it suitable for a wide range of standard applications, including systems with hundreds of atoms.
• The method is adopted as the new group default, replacing more expensive high-level methods in many cases.