Georg Kastlunger, Robert Stadler
An electrochemical STM is a rather innovative experimental method for measuring electron transport in single molecule nano-junctions, where for an atomistic interpretation of such experiments insight from density functional theory based calculations is needed. In this article we focus on coherent electron transport as one of the possible transport mechanisms, where the explicit influence of the solvent on the transmission function has only rarely been included for neutral molecules in the literature and to our best knowledge never before for redox-active systems. Naively one would expect a rigid shift of the transmission function with the oxidation state with respect to the Fermi energy of the leads but we find more complex behaviour because of equilibrium charge transfer between the molecule and the leads in dependence on the number of counter ions, which we investigate in the context of electronegativity theory. For adjusting the oxidation state of the redox-active molecule we correct for self interaction effects by fixing the charge on the counterions, which in our calculations mimic the effect of the gate in the STM setup, with two competing methods, namely the generalized $\Delta$ SCF technique and screening with solvation shells. 4A comparison of the two approaches allows for a physical interpretation of the oxidation state dependence of electron transport in this junction.
View original:
http://arxiv.org/abs/1211.7013
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