A (T) Correction for Multicomponent Coupled-Cluster Theory

TL;DR

This paper introduces a (T) correction for multicomponent CCSD, improving accuracy for proton affinities and energies while reducing computational cost through a targeted approximation.

Contribution

The work derives (T) and [T] perturbative corrections for multicomponent CCSD and proposes an efficient approximation focusing on mixed electron-nuclear excitations.

Findings

Perturbative corrections enhance accuracy over standard multicomponent CCSD.

The approximation reduces computational effort with minimal impact on protonic properties.

Benchmark results demonstrate improved energy and affinity calculations.

Abstract

The (T) and [T] perturbative corrections are derived for multicomponent coupled-cluster theory with single and double excitations (CCSD). Benchmarking shows that multicomponent CCSD methods that include the perturbative corrections are more accurate than multicomponent CCSD for the calculation of proton affinities and absolute energies. An approximation is introduced that includes only (T) or [T] contributions from mixed electron-nuclear excitations, which significantly reduces computational effort with only small changes in protonic properties.