Electronic structure of alkali-metal/alkaline-earth-metal fluorine beryllium borate NaSr3Be3B3O9F4 single crystal: DFT approach

• NaSr3Be3B3O9F4 is a direct wide band gap semiconductor.
• The band gap values are 4.82 eV (LDA), 5.16 eV (GGA), 6.20 (EVGGA) and 7.20 eV (mBJ).
• A strong hybridization were observed between the various orbitals.
• The electronic charge density were obtained in (1 0 1) and (0 0 −1) planes.

The electronic band structure, total and angular momentum resolved projected density of states for NaSr3Be3B3O9F4 are calculated using the all-electron full potential linearized augmented plane wave plus local orbitals (FP-LAPW + lo) method. The calculations are performed within four exchange correlations namely; local density approximation (LDA), general gradient approximation (PBE-GGA), Engel–Vosko generalized gradient approximation (EVGGA) and the recently modified Becke–Johnson potential (mBJ). Calculations suggest that NaSr3Be3B3O9F4 is a direct wide band gap semiconductor. The exchange correlations potentials exhibit significant influence on the value of the energy gap being about 4.82 eV (LDA), 5.16 eV (GGA), 6.20 (EVGGA) and 7.20 eV (mBJ). The mBJ approach succeed by large amount in bringing the calculated energy gap closer to the experimental one (7.28 eV). The angular momentum resolved projected density of states shows the existence of a strong hybridization between the various orbitals. In additional we have calculated the electronic charge density distribution in two crystallographic planes namely (1 0 1) and (0 0 −1) to visualized the chemical bonding characters.