Identification of LDA Optical Structure with Specific p-to-d Interband Transitions and Brillouin Zone Location: Important Clue on LDA Limitations

A comparison of the experimental optical spectra of DyP and DyBi with the predictions of band theory is presented. We show the important influence of the f-electrons on the optical behavior even when they do not directly enter in the optical transitions. The phospide and bismuthide are chosen because of their large difference in sizes. This can lead to significant differences in the d-electron crystal-field splitting, the width of pnictogen p-states and the f-screening of the d-electron crystal-field splitting. For both materials, we obtained experimental spectra that show considerable detailed structures which have very good one-to-one correspondence and, for some features, excellent agreement with the calculated spectra. Using different detailed visualization techniques we can associate well-defined optical structure features with specific p-to-d interband calculations in a specific part of the Brillouin zone. Comparison with the location in energy of the corresponding experimental features provides an important clue on when and why LDA works very well or less well.