Local structure, electronic and optical characteristics of Er3+-doped Y3Sc2Al3O12 garnet: a multi-scale exploration based on first-principles

Abstract In this study, the structural evolution, electronic properties, and optical characteristics of Er3+-doped Y3Sc2Al3O12 (YSAG) crystals were systematically investigated by the CALYPSO structure prediction methodology combined with density functional theory. The crucial findings are detailed as follows. 1) The ground state structure of Er3+:YSAG was determined. Er3+ ions substitute Y3+ sites to form [ErO8]13- coordination polyhedra with D2 point group symmetry, triggering space group transitions from Ia-3d to C222. The phonon spectrum and X-ray diffraction simulations confirmed the stability and accuracy of the structure. 2) Er3+ doping induced a band gap to narrow from 4.38 eV to 3.32 eV, attributed to the influence of the 4f electrons of Er3+ ions. Electron localization function and Bader charge analyses demonstrated the predominantly ionic nature of Er-O bonds. 3) Dielectric functions and absorption coefficients specified enhanced absorption in the vacuum ultraviolet region (25-35 eV) upon Er3+ incorporation. This study elucidated the structure-property relationships governing rare-earth doping effects in garnet-type laser crystals, providing fundamental theoretical insights for the microstructural design and performance optimization of rare-earth-doped laser materials.