Density Functional Theory (DFT) is not appropriate in predicting the band gap of the materials. However, which functional gives close value to the experimentally observed band gap of semiconductors? Any one of the following functional can give a close prediction of band gap?
LDA - PWC, VWN
GGA - PW91, BP, PBE, BLYP, BOP, VWN-BP, RPBE, HCTH.
What about the HOMO-LUMO gap? Can we use HOMO-LUMO gap (for non-periodic structures) instead of the gap observed in density of states?