On the other hand, cMD simulations rely on a force-field approach, which leads to a great speedup in calculations. Consequently, it allows for explicit treatment of solvent molecules, of course, at some cost in accuracy. While many force-fields exist, developed with either specific or general use, running a cMD simulation for metal containing systems requires the generation of custom parameters of the system at hand, to obtain reasonable results. While there are tools created for the parametrization of organic molecules, the parametrization of transition metal containing complexes is a more involved process, requiring a special approach. As metals can form very complex structures, with widely varying coordination numbers, there are no predefined atom parameters available in the widely used general force fields. A full parametrization of the metal center is therefore required. One tool available in the AmberTools suite, developed for parametrization of metal-containing biological systems, is the Metal Center Parameter Builder (MCPB). MCPB utilized a bonded model to describe the metal ion and its surrounding environment. This approach requires defining the bonded and nonbonded parameters of the force field, for the metal atom and its ligands. These parameters entail structural information, force constants and potentials for bonds, angles and dihedrals as well as partial charges and van der Waals parameters. They are generated based on either experimental or QM optimized structures, by deriving their values from force constants and partial charges. We would like to stress here that the force field parameters are generated in such way that the QM optimized structure is retained. While using a bonded model as implemented in MCPB provides accurate results for many different (transition-)metal containing complexes, the generation of parameters is an intricate process and error prone, due to a lot of user intervention required.