On the Position of the Highest Occupied Molecular Orbital in Aqueous Solutions of Simple Ions

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Abstract

The energies of the highest occupied molecular orbital (HOMO) of four simple microsolvated aqua ion clusters (Na+, Ag+, Cl, CN) are computed for varying numbers of water molecules. Extrapolating to infinite hydration numbers we find that these energies approach a value of −6 eV. This limiting one-electron energy is within a margin of ±1 eV independent of the character of the ion and is 4 eV lower compared to the estimate obtained for the HOMO energy of the ions in aqueous solution under periodic boundary conditions. We argue that this discrepancy must the attributed to a shift in the reference of the one-electron potential of the periodic solvent model.

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