Water molecule was chosen as the QM subsystem in both model systems where we used Troullier-Martins 34 pseudopotentials and the wavefunctions were expanded in a plane wave basis set with 70 Ry cutoff. Martyna-Tuckerman Poisson solver was used to decouple the QM long-range electrostatic interactions, thus removing the periodicity effects for the QM subsystem. As a requirement for the Martyna-Tuckerman method, we use a cubic QM supercell of size a = 21 Å to expand the wavefunctions for the QM water molecule, which is approximated to be at least twice as big as the biggest dimension of the QM subsystem. The exchange-correlation part of the KS-DFT Hamiltonian was described by the BLYP functional. The MM monomer was described using the AMOEBA force field. No periodic boundary conditions were applied for the MM subsystem. A combination of a DIIS algorithm was used for optimizing the QM density, and a PCG algorithm with tight convergence criteria of ≈ 10 -8 Debye/atom was used on the Tinker-HP side.