Physical Principles of Constructing Hybrid QM/MM Methods

Abstract

Constructing hybrid QM/MM methods and intersubsystem junctions in particular is an active area of research. The recipes proposed in this area are not sequentially derived from any adequate picture of electronic structure that leads to various numerical problems. We proposed the APSLG scheme as a basis for derivation of the MM-type description relying upon proven transferability of electronic structure parameters and explicit variational estimates of the one-electron states. Based on this we derived MM force fields for alkalies and amines. The QM/MM junctions then appear from the same analysis but with the difference that some part of the system is assumed to be treated by QM. The explicit formulae for the QM parameters pertinent to the boundary atom as well as for additional forces and torques acting upon the MM neighbours of the boundary atom are given.