 Empty lattice approximation

The Empty Lattice Approximation (ELA) is a theoretical model used in solid-state physics and condensed matter physics to simplify the understanding of electron behavior in a periodic lattice structure, such as a crystal. In this approximation, the effects of the lattice potential are neglected, and the electrons are treated as if they are free particles moving in an "empty" space, without interacting with the periodic potential created by the lattice ions.