New Theoretical Insights into the Crystal-Field Splitting and Transition Mechanism for Nd³⁺-Doped Y₃Al₅O₁₂

There has been considerable research interest paid to rare-earth transition-metal-doped Y₃Al₅O₁₂, which has great potential for application as a laser crystal of new-type laser devices because of its unique optoelectronic and photophysical properties. Here, we present new research conducted on the structural evolution and crystal-field characteristics of a rare-earth Nd-doped Y₃Al₅O₁₂ laser crystal by using the CALYPSO structure search method and our newly developed WEPMD method. A novel cage-like structure with a Nd³⁺ concentration of 4.16% is uncovered, which belongs to the standardized C₂₂₂ space group. Our results indicate that the impurity Nd³⁺ ions are likely to substitute the Y³⁺ at the central site of the host Y₃Al₅O₁₂ crystal lattice. The laser emission ⁴F_3/2 ⃗ ⁴I_11/2 occurring at 1077 nm is in accord with that of the experimental data. By introducing the proper correlation crystal field, three transitions, ⁴G_5/2 ⃗ ⁴I_9/2, ⁴F_7/2 ⃗ ⁴I_9/2, and ⁴S_3/2 ⃗ ⁴I_9/2, are predicted to be good candidates for laser action. These findings can provide powerful guidelines for further experiments of rare-earth-metal-doped laser crystals.