Lattice relaxation at metal surfaces: An electrostatic model

Surface relaxation in metals is investigated via an electrostatic model, using an iterative scheme allowing for the participation of many layers in the relaxation process. Comparative studies of surface relaxation are performed for the low-index faces of Al, Li, Na, and Cu, using three models for the electronic density: (a) step function, (b) exponential, (c) Lang-Kohn. The results demonstrate the importance of multilayer relaxation mechanisms, and the sensitivity of the results to the model of the surface electronic density. For the exponential density profile, simple pseudopotential corrections are also included and shown to have significant effects. The relaxation trends predicted are consistent with available results obtained by analyses of low-energy-electron-diffraction data.