Kronig-Penney Band Structure

cos(ka) = cos(αa) + (P/αa)sin(αa) — crank up the barrier and watch the free-electron parabola fracture into forbidden gaps.
P = 0.0 (free electron)
3 bands
P = 0.0
Band 1 top = π²
Gap 1 width = 0.000
Type = Metal (no gaps)