Hi, I just can't understand the basics with BZ. How do I find the shortest distance to the BZ boundary, how do I compare the electron energy between the last electron in the 1st BZ with the first electron in the 2nd BZ? I think I need a visual how to calculate these things, does anyone know any good site with illustrations? Here's an example: Q: For what minimum electron concentration Z does the free electron Fermi sphere touch the first Brillouin zone boundary of a BCC metal? A: Calculating the primitive reciprocal lattice vectors b_i of BCC we find the shortest distance to the BZ boundary |b_i|/2 = √2(π/a). How do I know the shortest distance is |b_i|/2? From here I know how to finish. If someone could show me some examples how to solve these types of questions I would be grateful! Sorry for any grammatic errors, English is not my native language.