In this section, the one-electron Schrödinger equation is used to solve the electron wave functions and energy states for a one-dimensional (1-D) periodic lattice. The periodic potential V(x) for the 1-D lattice is shown in Figure 4.1a. The Kronig-Penney model shown in figure 4.1b is used to replace the periodic potential of a 1-D crystal lattice with a delta function at each lattice site. In this model, it is assumed that V(x) is zero everywhere except at the
atomic site, where it approaches infinity in such a way that the integral of V(x)dx over the potential barrier remains finite and equal to a constant C. Inside the potential barrier, the electron wave functions must satisfy the one-electron Schrödinger equation, which is given by