Al(III) Hydration Revisited. An ab Initio Quantum Mechanical Charge Field Molecular Dynamics Study

To assess the novel quantum mechanical charge field (QMCF) molecular dynamics (MD) approach, two simulations of hydrated Al(III) have been carried out, as this system proved to be a well-suited test case for hybrid ab initio/molecular mechanics simulations. Two different population analysis schemes according to Mulliken and Löwdin have been applied to evaluate the atomic charges in the QM region. It is shown that the QMCF MD approach yields a substantially improved description of the system and that, due to the fact that solute−solvent potentials can be renounced, the QMCF MD framework is a more convenient approach to investigate solvated systems compared to conventional ab initio QM/MM MD approaches.