Coupled cluster/molecular mechanics method: Implementation and application to liquid water

In this paper, we present theory and implementation of the first method which combines coupled cluster and molecular mechanics (CC/MM) theory. By introducing the interactions between the solute (QM) and the solvent (MM) molecules into a coupled cluster Lagrangian, we calculate interaction and solvation energies of condensed phase molecules. Also, we derive a hierarchy in the coupling between the two subsystems and thereby study the importance of including the solvent polarization directly into the optimization conditions of the solute wave function for calculation of energies. The method is tested on the water dimer. Furthermore, calculations of the interaction and solvation energies of liquid water are presented.