In a band structure calculation, the dispersion relation for electrons is found to be 6, = plcosk,a + cosk,a + cosk,a) where ß is a constant and a is the lattic

In a band structure calculation, the dispersion relation for electrons is found to be 6, = Plcosk,a + cosk,a + cosk,a) where ß is a constant and a is the lattice constant. The effective mass at the boundary of the first Brillouin zone is h C)2a (a) (b)4 Spa Sa2 d) 3pa