Unformatted text preview: each well is U and its width a /5. a. Calculate the values of the first three energy gaps. Compare the magnitudes of these gaps. b. Evaluate these gaps for the case of U = 5 eV and a = 4Å. 3. Using the solution for the energy bands near the zone boundary in the presence of a weak crystal potential show that the electron velocity is parallel to the Bragg plane. Since the gradient is perpendicular to the surfaces on which a function is constant, this fact allows us to conclude that the constant energy surfaces (such as the Fermi surface) at the Bragg plane are perpendicular to that plane....
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 Spring '08
 WORMER
 Atom, Electron, Energy, Work, Condensed matter physics, Reciprocal lattice, weak crystal potential

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