Fig. 3. DFT calculation and ELF maps for La₄GeO₈:Bi³⁺ phosphor.

a–d Projected electronic densities of states (PDOSs) for three types of La sites, which are obtained via DFT calculations, where a and b are without oxygen vacancies and c and d are with oxygen vacancies. e Crystal structure of Bi³⁺-doping into various La³⁺ sites and the electron localization function (ELF) maps without (up) and with (down) oxygen vacancies in three La sites, where the purple, blue, green and red spheres represent Bi, La, Ge, and O atoms, respectively. f A schematic diagram of the transition energy levels of Bi replacing La without and with oxygen vacancies (i–iii) between the valence band and the conduction band. g The Gaussian fitting peak of the representative LGO:0.007Bi³⁺ sample