O–O hemi-bonding in cationic water clusters: Benchmarks from DFT, PNO-LCCSD(T), and FN-DMC

Water cluster cations serve as prototypical models for ionized aqueous environments and provide an ideal platform for examining the stability of O-O hemi-bonded motifs. Despite extensive studies, the relative energetics of hemi-bonded and proton-transferred structures, as well as their dissociation behavior, remain challenging to describe accurately. In this work, we present a systematic benchmark study of cationic water clusters (H2O)n+ (n = 2-8), with particular emphasis on O-O hemi-bonded sys