The local structure and electronic properties of Ho3+-doped BaY2F8: A first-principles method

Trivalent rare-earth Ho3+ doped barium yttrium fluoride (BaY2F8) has attracted a great deal of attention because of its excellent properties in many advanced lasers and other new material applications. However, the clear crystal structure of the Ho3+-doped BaY2F8 system (Ho:BYF) is still uncertain. Hence, through the CALYPSO structure search method, the first-principles study has been carried out on the structure evolution of the trivalent holmium ion (Ho3+) doped BaY2F8. The results indicate that the Y3+ ions in the host lattice are likely to be occupied by the doped Ho3+ ions, forming the [HoF8]5- polyhedra with C2 site symmetry. We successfully demonstrate the lowest energy structure of BaY2F8 heavily doped with Ho3+ ions is a brand-new structure having a standardized monoclinic P2 phase for the first time. According to the electronic structure calculation, the band gap value of Ho3+-doped BYF is about 5.73 eV, which is smaller than approximately 7.19 eV of pure BYF, indicating that both of them maintain insulation. The understanding of rare-earth Ho3+ ions doped crystal has been enriched from the perspective of theoretical calculation. The BaY2F8 crystal doped Ho3+ ions is expected to be applied in biomedical, laser communication and other fields. These provide a clear idea for grasping the structural evolution and exploring the properties when meeting other rare-earth-doped materials.