Toward more efficient density‐based adaptive QM/MM methods

Abstract

Adaptive QM/MM (quantum mechanical/molecular mechanical) methods repartition molecules on‐the‐fly into the QM and MM regions based on a partitioning criterion. A density‐based partitioning scheme offers a unique way of carrying out QM and MM assignments on the presence/absence of (non) covalent interactions between non‐QM core molecules and the QM core. Here, we present two improvements to promote our density‐based adaptive partitioning strategy for adaptive QM/MM calculations. First, bond formation/breaking processes between non‐QM core molecules and the QM core are monitored using a density‐based descriptor, to define an adaptive QM core region on the fly. Second, the density‐based adaptive QM/MM partitioning scheme is made efficient enough for large systems by utilizating an adaptive search region and a Voronoi style‐partitioning scheme. The adaptive search region is used to preselect the subset of molecules that may interact strongly enough with the QM core region, and then a density‐based interaction calculation is only carried out on this subset. A Voronoi style‐partitioning scheme achieves an efficient assignment of the density‐based interactions.