FCC Comb Potential

This animation shows how the band structure changes as the amplitude of the periodic potential grows. The potential is a 3-D comb with large amplitude negative peaks at the fcc Bravais lattice points. The amplitude of all of the Fourier coefficients $U_G$ are the same. For $U_G = 0$, the band structure is the same as for the empty lattice approximation. As the amplitude of the potential increases, the lowest band splits off and the upper bands reconfigure so that they take nearly the form of the empty lattice approximation again.

	Empty lattice approximation
$U_G$ = -0