Modeling the UV absorption spectrum of the hydroxyl anion in water

In this work, the experimental UV absorption spectrum of water in alkaline conditions has been modeled by capturing the most relevant water molecular clusters, selected by Principal Component Analysis on the structures sampled by classical Molecular Dynamics simulations, and adding the effect of the environment using a QM/MM procedure, the Perturbed Matrix Method. Such an approach allowed the treatment of the relevant molecular clusters with high-level QM methods, while correctly including the effect of the environment, both aspects necessary to accurately reproduce the wavelength of the absorption maximum and the intensity of the experimental spectrum.