Table 1.

Ionization energy I, electron affinity A, and fundamental gap G=IA of an infinite linear chain of H2 molecules, evaluated by extrapolation from finite chains, and the band edges εHO, εLU and band gap g=εLUεHO, in the LSDA (2), PBE GGA (4), SCAN meta-GGA (5), and HSE06 range-separated hybrid (8) functionals

eV(I+A)/2IHOALUGg
LSDA1.653.143.130.160.172.982.96
PBE1.673.243.230.090.103.153.13
SCAN1.683.333.310.010.023.323.29
HSE061.823.923.91−0.29−0.284.214.18
  • The extrapolated band energies agree closely with those from a periodic-boundary-condition calculation (shown). (I+A)/2, the energy difference from the gap center to the vacuum level (15), depends only weakly on the approximation.