QM/MM description of periodic systems

A QM/MM implementation for periodic systems is reported. This is done for the case of molecules and for systems with two and three-dimensional periodicity, which is suitable to model electrolytes in contact with electrodes. Tests on different water-containing systems, ranging from the water dimer up to liquid water indicate the correctness of the scheme. Furthermore, molecular dynamics simulations are performed, as a possible direction to study realistic systems.