Energy bands and gaps near an impurity

• Energy bands can bend near an impurity in the host lattice.
• We confirm possibility of energy band bending by using Kronig–Penney model.
• The impurity can have profound effect on wave function structure.

It has been suggested that in the neighborhood of a certain kind of defect in a crystal there is a bend in the electronic band. We confirm that this is indeed possible using the Kronig–Penney model. Our calculations also have implications for photonic crystals.