Surface properties in an external electric field

This paper reviews recent calculations on the effect of an external electric field on surface electronic properties, in particular using the embedding method for solving the Schrödinger equation at the surface. The shape of the screening charge and its field dependence are discussed, and the results are compared with experiments in which the image plane is determined. The force on the surface atoms in the field is given in terms of an effective charge, which also determines the work-function variation with surface displacements. This relationship can lead to a surface instability if the effective charge is big enough.