Application of transfer hamiltonian quantum mechanics to multi-scale modeling

In quantum mechanical/classical mechanical (QM/CM) partitioning methods for multi-scale modeling, one is often forced to introduce uncontrolled phenomenological effects of the environment (CM) in the quantum (QM) domain, as ab initio quantum calculations are computationally too intensive to be applied to the whole sample. We propose a method in which two qualitatively different components of the information about the state of the CM region are incorporated into the QM calculations. First, pseudoatoms constructed to describe the chemistry of the nearest-neighbor exchange interactions replace the atoms at the boundary of the CM and the QM regions. Second, the remaining effect of the CM bulk environment due to long-range Coulombic interactions is modeled in terms of dipoles. We have tested this partitioning method in a silica nanorod and a three-membered silica ring for which ab initio quantum data for the whole system are available to assess the quality of the proposed partitioning method.