Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 14: Topical session: Interface-Controlled Microstructures: Mechanical Properties and Mechano-Chemical Coupling - Electro- and mechno-chemical coupling

MM 14.1: Vortrag

Montag, 20. März 2017, 15:45–16:00, BAR 205

Electrocapillary coupling at metal surfaces from first principles — •Anja Michl1, Jörg Weissmüller2,3, and Stefan Müller11Hamburg University of Technology, Institute of Advanced Ceramics — 2Hamburg University of Technology, Institute of Materials Physics and Technology — 3Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Materials Mechanics

The surface stress f of metallic surfaces reacts sensitively to excess charge q. This response can be characterized by the electrocapillary coupling parameter ς=df/dq. Due to their high surface-to-volume ratio, nanoporous metals respond with a macroscopic deformation to electric charging in electrolyte, which makes these materials interesting alternatives to conventional actuators. Exploiting a Maxwell relation, we have determined ς in terms of the response of the work function to in-plane strain for several metal surfaces, focusing mainly on the response of sp-bonded metals. It is found that aluminum surfaces exhibit positive coupling coefficients, whereas the other sp-bonded metals show the usual negative sign known from previous experimental and theoretical studies of clean transition metal surfaces. In addition, we investigate the impact of excess charge on surface structure and bonding via ab-initio simulation of metal surfaces in an external electric field in order to gain further insight into the underlying mechanisms. Both the direct effect on the surface stress via charging of the bonds and the indirect effect resulting from the charge-induced relaxation will be analyzed and discussed in relation to the trends of the determined coupling coefficients.

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