The potential-induced surface reconstruction of Au(1 0 0) was studied by a combination of density functional theory (DFT) and thermodynamic considerations. On the basis of realistic models for the reconstructed surface ((5 x 1) and (7 x 1) unitcells), in which a hexagonal overlayer was located above the bulk-truncated Au(1 0 0) surface, we found that applying an electric field causes a slight lifting of the overlayer, leading to a stronger surface buckling than without electric field. Using experimental cyclovoltammetry measurements we were able to relate the electric field applied in our calculations to the electrode potential. The resulting surface free energy curves showed a transition from the hexagonal-reconstructed surface phase to the non-reconstructed structure between +0.5 and +0.6V (versus SCE-electrode) depending on the ion concentration in the electrolyte. Higher potentials values are required at lower electrolyte concentrations. (c) 2006 Elsevier Ltd. All rights reserved.