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Introduction

Band theory is based on quantum mechanics and comes from the theory of molecular orbitals.If multiple atoms are brought together into a molecule their atomic orbitals will combine to form a layer of molecular orbitals each with a different energy . For the giant molecule the energy levels are so close that they can be considered to form a continuum. Fiugure 1 shows the different layer of the band theory such as conduction band, band gap and valance band.

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