A design for a DFT computational normal hydrogen electrode
|Location: Hörsaal A (1.3.14)
Time: Monday, November 22, 2010, 14 h s.t.
The Density functional Theory based Molecular dynamics (DFTMD) method aims at treating all of a condensed phase model system at the same level of theory. Progress in computational methodology and hard ware performance has steadily increased system size and time window accessible to DFTMD. The state of the art for models of aqueous systems is a length scale of 1 to 2 nm and time scale of 10 to 50 ps. This size of a systems is sufficient to study the structural and dynamical properties of a large class of organic molecules and inorganic complexes in full solution. However, the DFTMD computation of thermochemical constants, such as acidity constants and reduction potentials faces still serious challenges. This holds in particular for the calculation of potentials differences accross electrochemical interfaces. A first step in an electrochemical extension of DFTMD is the design of a computational normal hydrogen electrode (NHE). In this talk we will present such a scheme based on reversible insertion of protons and electrons in periodic condensed phase model systems. The key constraint in the development of this scheme is the unified treatment of deprotonation and oxidation which enables us to compute reaction free changes of deprotonation coupled oxidation reactions or the reverse, protonation coupled reduction. The normal hydrogen electrode is an example of a protonation coupled reduction, with the reduction and protonation taking place in different compartments of the system. The results for the pKa and NHE potentials of a (still small) class of simple organic and inorganic molecules will be presented and as well as a first application to a metal oxide (TiO2) water interface.
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