Electronic structure of mono-, di- and tri-fluorides: Hybrid functional and modified Becke-Johnson potential calculations

Metal fluorides are ionic compounds with intriguing properties and a wide range of industrial and technological applications. In this paper, we present the results of an extensive first-principles study of the electronic band structure of nineteen mono-, di-, and tri-fluorides. Four approaches are employed in this study: LDA, pseudopotential and all-electron modified Becke-Johnson (mBJLDA@PP and mBJLDA@AE) potentials, and Yukawa Screened Hybrid Functional (YS-PBE0). The mBJLDA and YS-PBE0 band gaps are in good overall agreement with the available G0W0 results and experimental data, which ensures the reliability of the provided predictions for systems where accurate band gaps are lacking. The LDA and YS-PBE0 upper valence band (UVB) widths are very close to each other, and these results are, in general, slightly smaller than the G0W0 results and experimental data. It is shown that the band gap and UVB width vary with F-F distance, and distinct trends are identified. The LDA density of states of the UVB for the alkali and alkaline-earth fluorides are analyzed and compared to the available XPS and XES spectra. It is found that the LDA approach provides accurate results for peak intensities as well as satellite peak positions relative to the main peak. A strong correlation is demonstrated between the adopted crystal structures of the considered fluorides and their bond ionicity.