Simplified self-interaction correction applied to the energy bands of neon and sodium chloride

The local-density approximation (LDA) for the exchange-correlation potential underestimates the fundamental energy gaps of insulators by about 40%. When a simplified self-interaction correction (SSIC) is applied to the band structures of Ne and NaCl, vast improvements over LDA are found in the gaps, with little change in the valence-band widths or conduction-band structures. Because it is applied directly to the Bloch orbital representation, SSIC is very easy to incorporate into LDA computer codes. Results are also reported using the Langreth-Mehl (LM) generalized gradient correction to LDA. The LM potential, which we regard as a close approximation to the exact Kohn-Sham potential, yields band structures very close to those of LDA.