First-principles LDA + U calculations and luminescence study of YNbO 4

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From the article :

Both Y([Kr]5s24d1) and Nb ([Kr]5s14d4) atoms have incomplete d-orbitals.  The quantum eects contributed by these strongly correlated d-electrons can
be properly treated using the LDA+U approach.

 There are two free parameters in the LDA+U calculation, namely, the exchange parameter J and the Hubbard energy
U. The exchange parameter J, despite having no efects on the overall DOS prole, will cause the band gap to become narrow.  Thus we set J to zero in our LDA+U
calculations.  The Hubbard energy U in the LDA+U calculations is manually tuned so that the resultant band gap from the LDA+U calculations agrees with that obtained by the experiments.

The self-interaction correction (SIC) variant of the LDA+U approach,  introduced by Anisimov et al.  [25] with an approximate correction to the self-interaction, is used.