2. Surface structure

A central issue in current surface physics concerns the detailed understanding of the electronic structure of surfaces. At the "theoretical" level, simulations are based on a general approach similar to that of the volume, where the effective potential approximation is used to solve a Schrödinger equation describing an electron close to the surface, subjected to the action of an average potential or electric field due to the ionic cores and all the other electrons considered as an "electronic cloud". Compared with the volumetric electron structure, the problem is considerably more complicated for the surface, as we can no longer rely on three-dimensional translational symmetry, which only exists in the plane of the surface. Perpendicular to this, periodicity is broken, and the perpendicular k _⊥ component of the electron's k wave vector is no...