Consistent Analytical Second Derivatives of the Kohn–Sham DFT Energy in the Framework of the Conductor-Like Screening Model 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,
as both 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 the COSMO
charges. This work introduces an efficient implementation for consistent
analytical second derivatives of the electronic energy with COSMO-GCM
in the framework of the Kohn–Sham density functional theory.
This is used to investigate the infrared spectroscopy of amino acids
in aqueous solution, where the impact of pH on the molecular structure
and vibrational spectra is examined. Furthermore, the structure and
stability of selected all-metal aromatic cluster ions are assessed.