Canonical and DLPNO-based composite wavefunction methods parametrized against large and chemically diverse training sets. 2. Correlation consistent basis sets, core-valence correlation, and F12 alternatives

TL;DR

This paper develops advanced wavefunction composite methods with improved basis sets and correlation treatments, achieving high accuracy for diverse molecules at reduced computational cost.

Contribution

It introduces cc-G4-type methods with complete basis set extrapolation and DLPNO variants, significantly enhancing accuracy and efficiency over previous approaches.

Findings

WTMAD2 below 1 kcal/mol on GMTKN55 benchmark

Valence correlation dominates improvements, core-valence less critical

DLPNO methods enable large molecule calculations efficiently

Abstract

A hierarchy of wavefunction composite methods (cWFT), based on G4- type cWFT methods available for elements H through Rn, was recently reported by Semidalas and Martin [J. Chem. Theor. Comput. 2020, 16, 4238]. We extend this hierarchy by considering the inner-shell correlation energy in the second-order Moller-Plesset correction and replacing the Weigend-Ahlrichs def2-mZVPP(D) basis sets used in the aforementioned paper with complete basis set extrapolation from augmented correlation consistent core-valence triple-zeta, aug-cc-pwCVTZ(-PP), and quadruple-zeta, aug-cc-pwCVQZ(-PP), basis sets, thus creating cc-G4- type methods. For the large and chemically diverse GMTKN55 benchmark suite, they represent a substantial further improvement and bring WTMAD2 (weighted mean absolute deviation) down below 1 kcal/mol. Intriguingly, the lion's share of the improvement comes from better capture of valence correlation; the inclusion of core-valence correlation is almost an order of magnitude less important. These robust correlation consistent cWFT methods approach the CCSD(T) complete basis limit with just one or a few fitted parameters. Particularly the DLPNO variants such as cc-G4-T-DLPNO are applicable to fairly large molecules at modest computational cost, as is (for a reduced range of elements) a different variant using MP2-F12/cc-pVTZ-F12 for the MP2 component.