2. Concepts for calculating the electronic structure of solids

In the following paragraphs, we review the concepts underlying the methods used to calculate the electronic structure of solids before demonstrating how these concepts can be extended to the surfaces of solids.

Every solid is necessarily bounded by a surface that encloses its volume. To study only the volumetric properties of a crystal, it can be modeled as an infinite periodic repetition of unit cells in space, thereby avoiding surface-related issues. We then say that we are dealing with an infinite three-dimensional (3D) solid. We can also use the Born-von Karman cyclic boundary conditions to eliminate surfaces (article Electronic Structure of Solids in this section).