5- and 6-membered rings: A natural orbital functional study

TL;DR

This study evaluates the effectiveness of the Global Natural Orbital Functional (GNOF) and its variant GNOFm in accurately capturing electron correlation in 5- and 6-membered rings, demonstrating their reliability and improvements over previous methods.

Contribution

The paper introduces and assesses the GNOF and GNOFm functionals for modeling electron correlation in molecular rings, showing their accuracy and robustness compared to benchmark methods.

Findings

GNOF and GNOFm accurately describe dynamic correlation in molecular rings.

GNOFm shows systematic improvements over GNOF.

Both functionals perform well across different basis sets.

Abstract

The Global Natural Orbital Functional (GNOF) provides a straightforward approach to capture most electron correlation effects without needing perturbative corrections or limited active spaces selection. In this work, we evaluate both the original GNOF and its modified variant GNOFm on a set of twelve 5- and 6-membered molecular rings, systems characterized primarily by dynamic correlation. This reference set is vital as it comprises essential substructures of more complex molecules. We report complete-basis-set limit correlation energies for GNOF, GNOFm, and the benchmark CCSD(T) method. Across the Dunning basis sets, both functionals deliver a balanced and accurate description of the molecular set, with GNOFm showing small but systematic improvements while preserving the overall robustness of the original formulation. These results confirm the reliability of the GNOF family and its ability to capture dynamic correlation effects.