Does basis set superposition error significantly affect post-CCSD(T) corrections?

TL;DR

This study evaluates the impact of basis set superposition error on post-CCSD(T) corrections across different benchmarks, finding it generally negligible, especially with larger basis sets and extrapolation techniques.

Contribution

It provides a comprehensive analysis showing that BSSE has minimal effect on post-CCSD(T) corrections in thermochemistry and noncovalent interactions, clarifying its significance in computational chemistry.

Findings

Counterpoise corrections to post-CCSD(T) are much less significant than to CCSD(T) interaction energies.

BSSE effects on connected quadruple substitutions are negligible.

Extrapolation methods effectively reduce BSSE impact on atomization energies.

Abstract

We have investigated the title question for both a subset of the W4-11 total atomization energies benchmark, and for the A24x8 noncovalent interactions benchmark. Overall, counterpoise corrections to post-CCSD(T) contributions are about two orders of magnitude less important than those to the CCSD(T) interaction energy. Counterpoise corrections for connected quadruple substitutions (Q) are negligible, and $(Q)_\Lambda - (Q)$ or $T_4 - (Q)$ especially so. In contrast, for atomization energies, the $T_3-(T)$ counterpoise correction can reach about 0.05 \kcalmol~for small basis sets like cc-pVDZ, thought it rapidly tapers off with cc-pVTZ and especially aug-cc-pVTZ basis sets. It is reduced to insignificance by the extrapolation of $T_3-(T)$ applied in both W4 and HEAT thermochemistry protocols. In noncovalent dimers, the differential BSSE on post-CCSD(T) correlation contributions is negligible even in basis sets as small as the unpolarized split-valence cc-pVDZ(no d).