Influence of Three-Body Effects on Halogen Bonding

TL;DR

This study introduces a new benchmark dataset for halogen-bonded complexes with a third partner, analyzing three-body effects and their physical origins using high-level quantum calculations and energy decomposition methods.

Contribution

The paper presents the 3BXB benchmark dataset and provides detailed analysis of three-body effects in halogen bonding using SAPT-based energy decomposition.

Findings

Two-body attractions are dominated by electrostatics or dispersion.

Three-body effects are mainly due to induction, which can be attractive or repulsive.

Wavefunction-based SAPT methods accurately recover reference energies.

Abstract

We construct a new noncovalent benchmark dataset 3BXB that combines halogen-bonded bimolecular complexes from the SH250 dataset [Kriz and Rezac, Phys. Chem. Chem. Phys. 2022, 24, 14794] with a third interacting partner, either H$_2$O or CH$_4$. The reference total and three-body interaction energies are computed at the CCSD(T) level. To shed light on the physical origins of binding and cooperativity in complexes of this kind, several symmetry-adapted perturbation theory (SAPT)-based energy decompositions were performed for both pairwise additive and nonadditive terms. We found that the two-body attractions in the 3BXB complexes are dominated by either electrostatics or dispersion, while the three-body effect is dominated by induction and can be either attractive or repulsive. An accurate recovery of reference interaction energies is attained by the wavefunction-based two-body SAPT variants including the $\delta$MP2 correction, combined with the SAPT(DFT) estimates of nonadditive induction and first-order exchange and any estimate of nonadditive dispersion. The values for the latter term are sometimes quite inconsistent between different approaches; fortunately, nonadditive dispersion is a relatively minor effect for complexes studied here, and all reasonable estimates lead to total interaction energies of similar accuracy.