Consistent analytical second derivatives of the Kohn–Sham DFT energy in the framework of the Conductor-like screening Model (COSMO) through Gaussian charge distributions

The use of implicit solvation models such as the conductor-like screening model (COSMO) in quantum chemical calculations is very common, both as a rough estimate of solvation effects as well as a general tool for stabilizing ionic molecular structures. In order to generate a smooth potential energy surface as well as consistent gradients, it is necessary to apply the Gaussian charge model (GCM) for COSMO charges. This work introduces an efficient implementation for consis- tent analytical second derivatives of the electronic energy with COSMO-GCM in the framework of Kohn–Sham density functional theory. This is used to investigate infrared spectroscopy of amino acids in aqueous solution, where the impact of pH on the molecular structure and vibrational spec- tra is examined. Furthermore, structure and stability of selected all-metal aromatic cluster ions are assessed.