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Solving the Schrodinger equation directly for a particle in one-dimensional periodic potentials

Solutions of time-independent Schrodinger equation for potentials periodic in space satisfy Bloch theorem. The theorem has been used to obtain solutions of the Schrodinger equation for periodic systems by expanding them in terms of plane waves of appropriate wave-vectors and then diagonalising the resulting Hamiltonian matrix. However, this method can give exact solutions only if an infinite number of plane-waves are used in the wavefunction. Thus the Schrodinger equation has not been solved exactly even for one-dimensional infinitely large periodic systems despite the simplification that the theorem provides. On the other hand, solutions of one-dimensional Schrodinger equation for finite systems are obtained routinely by using standard numerical techniques to integrate the Schrodinger equation directly. In this paper, we extend this approach to infinitely large systems and use Bloch theorem in a novel way to find direct exact numerical solutions of the Schrodinger equation for arbitrary one-dimensional periodic potentials. In addition to providing a different way of solving the Schrodinger equation for such systems, the simplicity of the algorithm renders it a great pedagogical value.