Counterpoise Correction and Charge Embedding as Antidotes for Delocalization Error in Density Functional Many-Body Expansion

Recent work has highlighted how integration grid and self-interaction errors (SIE) can lead to divergent density functional many-body expansion. While the pernicious effect of basis set superposition error (BSSE) on many-body expansion has been known for some time, this effect is compounded by SIE and is likely to play an even more important role. In this study, we demonstrate that elimination of BSSE through the counterpoise correction can simultaneously attenuate sensitivity of MBE to DFT grid errors and reduce MBE errors by more than 50%. We focus on the same ion–water clusters examined in recent studies and further demonstrate that when effects of BSSE and DFT grid errors are minimized, charge embedding can be an effective strategy for mitigating SIE to restore the convergent behavior of many-body expansion.