Revisiting Boron Cluster Dihydrogen Bonding: Improved Reference Energies and Benchmark of Localized Coupled Cluster and DFT Methods

Dihydrogen bonds involving boron clusters have gained significant attention in chemistry, biology, and medicine. The reference interaction energies of diH-norm and diH-linear datasets (J. Fanfrlík et al., ChemPhysChem 2020, 21, 2599), which include such bonds both in bent and linear configurations, have been re-evaluated at the gold level. This re-evaluation utilizes explicitly correlated MP2-F12 near the complete basis set limit, CCSD(F12*)/cc-pVQZ-F12, and a (T) correction from conventional CCSD(T)/haV{T,Q}Z calculations. Relative to the updated reference data, Fanfrlík's original reference shows very small root mean square deviations, resulting from significant error compensation between the [CCSD-MP2] and (T) high-level corrections. Furthermore, the revised reference is employed to assess the performance of various localized-orbital coupled-cluster approaches, such as PNO-LCCSD(T), DLPNO-CCSD(T1), and LNO-CCSD(T), at their respective “Normal”, “Tight”, “vTight”, and “vvTight” accuracy settings. For these methods, gradually increasing the basis set size and tightening the accuracy cutoffs improves their performance. For the dihydrogen bonds in diH-norm set, two cost-effective methods with no noticeable loss in accuracy are PNO-LCCSD(T)/Tight/haV{T,Q}Z and DLPNO-CCSD(T1)/TightPNO/CPS(6,7)/haV{T,Q}Z. On the other hand, for the diH-linear set, LNO-CCSD(T)/vTight/haV{T,Q}Z and DLPNO-CCSD(T1)/TightPNO/CPS(6,7)/haV{T,Q}Z are the recommended low-cost methods. Among the more economical density functional methods, r2SCAN-3c demonstrates remarkably good accuracy at a very cheap cost. Additionally, for hybrid and double-hybrid functionals, the incorporation of range separation significantly enhances performance.