Multicentered integrated QM:QM methods for weakly bound clusters: An efficient and accurate 2-body:many-body treatment of hydrogen bonding and van der Waals interactions

An efficient integrated QM:QM technique for the description of weakly bound clusters is presented. The computational technique described here takes advantage of the recently developed multicentered (MC) integrated QM:QM methods and reliably describes hydrogen bonding and van der Waals interactions by treating all 2-body interactions with a high-level QM method and the many-body interactions with a low-level QM method. Even for small clusters of He, Ne, HF, and water, the MC QM:QM methods are typically 1–3 orders of magnitude faster than the high-level method while introducing an error of less than 1% in the interaction energy.