How does one interpret band structures (i.e. E,k solution pairs for a given Hamiltonian) for a non-primitive cell? I was looking at these slides: http://www.tcm.phy.cam.ac.uk/castep/CASTEP_talks_06/clark2.pdf Slide 9 has the "normal" silicon band structure obtained with a primitive cell. Slide 11 uses a cubic cell and obtains a different band structure. Do they somehow contain equivalent information? I know zones fold over, but the non-primitive band structure actually seems to have a direct band gap at Gamma, while Si is known to have an indirect gap. How was this information lost?