The '''empty lattice approximation''' is a theoretical [[electronic band structure]] model in which the '''potential''' is defined not more precisely than '''periodic''' and '''weak'''. The empty lattice approximation describes a number of properties of energy dispersion relations of non-interacting '''[[Free electron model|free electrons]]''' that move through a '''[[crystal structure|crystal lattice]]'''. The energy of the electrons in the "empty lattice" is the same as the energy of free electrons. The model is useful because it clearly illustrates a number of the sometimes very complex features of energy dispersion relations in solids which are fundamental to all electronic band structures.
