Hi, I was hoping I could get some things cleared up. Recently my Solid State professor mentioned that we could simply, from the chemical formula, predict where the band crossings are going to be. For example, take LaFeAsO. Since La has a valency of +3, Fe of +3, As of -3, and O of -2, he deducted from the lattice (which is more or less cubic), that the band crossings are going to be primarily from the Fe. However, I'm completely lost as to why. Any help is appreciated!