Ab Initio Molecular Dynamics Simulation of a Medium-Sized Water Cluster Anion: From an Interior to a Surface Located Excess Electron via a Delocalized State

Abstract

We present a computational study of the structure and dynamics of an excess electron in a medium-sized water cluster aimed at addressing the question of interior vs. exterior solvation. Ab initio Born-Oppenheimer molecular dynamics simulations are performed within the DFT framework, employing a hybrid Gaussian and plane waves formalism together with the PBE exchange-correlation functional and norm-conserving pseudopotentials. The analysis of a 15 ps trajectory allows us to reach the following conclusions: (i) the excess electron is predominantly located at the cluster surface (even if it is initially placed in the interior), (ii) the computed electron binding energies correlate with the electron localization rather than with its bulk vs surface location, (iii) a dynamical interconversion between two different H-bond patterns around the electron is found. The computed electron binding energies and the most relevant features of the IR spectrum are in a very good agreement with previous experimental studies.