Investigation of the structure and luminescence mechanism of Tm³⁺-doped LiYF₄: New theoretical perspectives

The absorption and emission transitions of Tm³⁺-doped LiYF₄ have been extensively investigated due to the excellent properties and enormous applications of these materials as laser materials. However, the challenging issues regarding the local structure and luminescence mechanism have not been conclusively established to date. To address these challenges, the CALYPSO structure search method is employed, and the results first reveal the ground-state structure of Tm³⁺-doped LiYF₄, which crystallizes in the space group P4̅ (No. 81) of the tetragonal system. The Y³⁺ ions are replaced by Tm³⁺ ions, forming a local configuration of [TmF₈]⁵⁻. Furthermore, the complete Stark energy levels of Tm³⁺-doped LiYF₄ are predicted by using our newly developed WEPMD method, which provides preliminary preparation for further spectral exploration. Judd–Ofelt analysis is performed to evaluate the electric dipole transition intensities. Two prominent transitions, ³H₅ → ³H₆ (1223 nm) and ³H₄ → ³H₆ (801 nm), are predicted to be good candidates for near-infrared lasers. This study not only is useful for determining the luminescence properties of Tm³⁺-doped LiYF₄ but also offers an effective way to search for other rare-earth-doped lasing crystals for the future design of lasing materials. Copyright © 2019 American Chemical Society.