Automatic orbital pair selection for multi-level local coupled-cluster based on orbital maps

04 July 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

We present an automatic, orbital-map based orbital pair selection scheme for multi-level local coupled-cluster approaches that exploits the locality of chemical reactions and concentrates on the part of the molecule directly involved in the reaction. The previously introduced pair-selected multi-level extension to domain-based local pair natural orbital coupled-cluster with singles, doubles, and semi-canonical perturbative triples [DLPNO-CCSD(T0)] partitions the orbital pairs according to relative changes in pair correlation energies [J. Chem. Phys. 157, 064102 (2022)]. To this end, maps between localized orbitals are required which in turn require maps between the atoms of structures along reaction paths. So far, these atom maps have been manually determined, which can be a (human) time-consuming procedure. In order to automatize this procedure, we present an atom mapping algorithm based on the principle of minimum chemical distance that incorporates the orientation through dihedral angles. Within the methodology of this algorithm, linear assignment problems are addressed and explicitly solved, giving rise to the idea of considering the orbital mapping problem as such. This led to a new strategy to obtain orbital maps that proves advantageous over the previously used direct orbital selection. Along with a modified orbital pair prescreening, this results in an improved variant of the pair-selected multi-level DLPNO-CCSD(T0) method. For given combinations of pair selection thresholds, the performance of this approach is demonstrated for various reaction types showing a significant efficiency gain and accurate results due to beneficial, systematic error cancellation. The presented method operates in a black-box manner due to its fully-automatized algorithms with only the need to specify a single target-accuracy parameter. Core orbitals can be included in the correlation treatment in a computationally cheap way such that there is no need for the frozen-core approximation. Additionally, we demonstrate that basis set extrapolation techniques can be applied. In this context, the approach shows deficiencies for the use of large basis sets, especially with diffuse basis functions, which can be traced back to the semi-canonical triples correction.

Keywords

Multi-Level Coupled Cluster
Atom Mapping Algorithm
Reaction Energies

Supplementary materials

Title
Description
Actions
Title
Supporting Information for: "Automatic orbital pair selection for multi-level local coupled-cluster based on orbital maps"
Description
Detailed information on the treatment of dihedral angles and the choice of thresholds in the atom map construction, additional results for the pair-selected multi-level DLPNO-CCSD(T0) method, an example for an atom mapping found in the benchmark sets with an unusually large number of formed and broken bonds, as well as data for basis set extrapolation with aligned orbitals.
Actions

Comments

Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.