Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 45: Solid / liquid interfaces I

O 45.5: Talk

Wednesday, March 28, 2012, 11:30–11:45, A 060

On the accuracy of ion hydration energies - an ab-initio study — •Mira Todorova and Jörg Neugebauer — Department for Computational Materials Design, Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

An accurate prediction of hydration free energies of ions and molecules is crucial for modelling chemical, electrochemical and biochemical reactions in water and at water/material interfaces. Experimental measurements are performed on neutral solutions and the extraction of individual ion solvation free energies relies on assumptions, such as the tetraphenylarsonium tetraphenylborate (TATB) extrathermodynamic assumption [1]. This severely hinders the assessment of theoretical approaches to compute such data.

Extending an approach originally derived to describe charged defects and their concentration in semiconductors [2], revealed that the TATB extrathermodynamic assumption employed to obtain experimental free energies is incorrect, and provided criteria to judge the accuracy of calculated ion-hydration energies. Focusing on the hydration energy of H⁺(aq) and OH⁻(aq) individual free energy contributions to calculated ion hydration energies will be discussed.

[1] Y. Marcus, J. Chem. Soc., Faraday Trans. 1, 83, 339 (1987).

[2] C.G. Van de Walle and J. Neugebauer, J. Appl. Phys. 95, 3851 (2004).