r2SCAN-3c: An Efficient “Swiss Army Knife” Composite Electronic-Structure Method

Abstract

The recently proposed second revision of the SCAN meta-GGA density-functional approximation (DFA) {Furness et al., J. Phys. Chem. Lett. 2020, 11, 8208-8215, termed r<sup>2</sup>SCAN} is used to construct an efficient composite electronic-structure method termed r<sup>2</sup>SCAN-3c, expanding the "3c'' series (hybrid: HSE/PBEh-3c, GGA: B97-3c, HF: HF-3c) to themGGA level. To this end, the unaltered r<sup>2</sup>SCAN functional is combined with a tailor-made <br>triple-zeta Gaussian AO-basis as well as with refitted D4 and gCP corrections for London-dispersion and basis-set superposition error. The performance of the new method is evaluated for the GMTKN55 thermochemical database covering large parts of chemical space with about 1500 <br>data points, as well as additional benchmarks for noncovalent interactions, organometallic reactions, lattice energies of organic molecules and ices, as well as for the adsorption on polar salt and non-polar coinage-metal surfaces. These comprehensive tests reveal a spectacular performance and robustness of r<sup>2</sup>SCAN-3c for reaction energies and noncovalent interactions in molecular and periodic systems, as well as outstanding conformational energies, and consistent structures. At just one tenth of the cost, r<sup>2</sup>SCAN-3c provides one of the best results of all semi-local DFT/QZ methods ever tested for the GMTKN55 benchmark database. Specifically for reaction and conformational energies as well as for noncovalent interactions, the new method outperforms hybrid-DFT/QZ approaches, compared to which the computational savings are even larger (factor 100-1000).<br>In relation to other "3c'' methods, r<sup>2</sup>SCAN-3c by far surpasses the accuracy of its predecessor B97-3c at only about twice the cost. The perhaps most relevant remaining systematic deviation of r<sup>2</sup>SCAN-3c is due to self-interaction-error, owing to its mGGA nature. However, SIE is notably reduced compared to other (m)GGAs, as is demonstrated for several examples. After all, this remarkably efficient and robust method is chosen as our new group default, replacing previous low-level DFT and partially even expensive high-level methods in most standard applications for systems with up to several hundreds of atoms.<br><br>

eQE 2.0: Subsystem DFT Beyond GGA Functionals

“…Following this release, we will turn to further improve eQE's performance implementing new features which may include (but not limited to) development of new nonadditive XC functionals, especially the latest SCAN variants (such as: r2SCAN [83,84], r2SCAN+ [85,86], SCAN+rVV10 [87]). We will also continue to develop more accurate KEDFs for both nonadditive functionals for embedding and for approximating the kinetic energy density used in deorbitalized meta GGA functionals.…”

Thermal Decomposition Mechanisms of Volatile Molybdenum(VI) Bis-Imides

“…104 Guess geometries were either extracted from single-crystal X-ray diffraction structures or drawn by hand in Avogadro 1.2.0. 105 Geometry optimizations and analytic frequency calculations were performed with the composite density functional theory (DFT) method r 2 SCAN-3c 89 which combines the r 2 SCAN meta-generalized gradient approximation (mGGA) exchange-correlation functional, 106 refitted charge-dependent D4…”

“…Recently, very efficient and highly accurate methods have become available in ORCA 5 88 that enabled us to investigate many reasonable decomposition mechanisms without needing to resort to reduced model systems or unreliable theoretical methods. We used the efficient implementation of the composite density functional theory (DFT) method r 2 SCAN-3c 89 to obtain accurate geometries with a low computational cost, and the climbing image nudged-elastic band (NEB-CI) 90 method to quickly find minimum energy paths (MEPs) and good guess geometries of transition states (TSs) for complicated mechanisms. All proposed reaction mechanisms were confirmed by intrinsic reaction coordinate (IRC) analysis.…”

Primary vs Secondary: Directionalized Guest Coordination in β-Cyclodextrin Derivatives

“…Due to the large sample size and the unconstrained exploration of configurational space at the high temperature, this reference set covers relevant regions and further adding samples leads to negligible changes of the refitting results. The target level used for the large host molecule is BLYP [69][70][71][72] /def2-SVP with the latest D4 dispersion correction 73,74 considering its good performance in modelling various properties (including non-covalent interactions) among pure functionals, while for the small guest molecules a higher-level method, the r 2 SCAN-3c 75,76 composite scheme, is selected. The resolution-of-theidentity approximation 77,78 is always employed in ab initio calculations.…”