First-principles simulation of a charged electrode: the electronic structure of a Ag(001) surface under the influence of an external electrostatic field

Abstract

Results of local density full-potential linearized-augmented-plane-wave (FLAPW) calculations for an 11 layer slab of a Ag(001) surface under the influence of an external electrostatic field are presented. For the simulation of a charged electrode a self-contained model is designed by calculating the external electrostatic potential acting on the surface arising from an external charge distribution which should represent the electrolyte. In order to describe this external charge density distribution we make use of the Gouy-Chapman model (which is well known in electrochemistry) and calculate the corresponding potential by separating the electrolyte into two parts with different dielectric constants, inside and outside the outer Helmholtz plane. This calculated potential is incorporated as an external potential into the local density equations for solving the quantum mechanical equations of the Ag(001) surface. From the self-consistent solutions obtained by the FLAPW method, we evaluate the electronic charge distribution in the region of the metal surface, determine the mean electrostatic potential inside the electrode and the work function dependence on the applied field. Furthermore, we study the influence of the external field on some characteristic surface states (Stark shift). We conclude that our first-principles model for treating charged electrodes seems to represent the available experimental data in a reliable manner.