An alternative method to calculate surface states in crystals

An alternative method to calculate surface states in crystals is presented based on solving a one-dimensional problem in the direction perpendicular to the crystal surface and a nearly-free-electron (N.F.E.) model in the direction parallel to the surface. The potential is calculated making use of pseudopotential and a study of the structure factor. As an example we consider the case of the (111) surface orientation of Ge and Si, obtaining two bands of surface states separated 0.55 eV and 0.43 eV at the X and L points of the two-dimensional B.Z. This splitting is achieved without considering surface rearrangement.