Tb/Sm co-doping mediated luminescence regulation in Mg-based LiMgPO4 with insights from ab initio calculations and experimental investigation

• The specific occupation of equivalent Mg sites and repulsive interaction between Tb³⁺ and Sm³⁺ serve as the atomic-scale origin for optimal luminescence. • A complete "repulsion → dispersion → energy migration → quenching'' chain is established, bridging the gap between atomic-scale interactions and macroscopic TL and OSL properties. • The concentration-dependent energy localization was deciphered, demonstrating that doping concentration modulates trap parameters (E, s) without creating new types of traps. • An integrated approach of first-principles calculations and experimental validation was employed, providing a transferable framework for studying Mg-based phosphors. This study systematically investigates the effects of Tb/Sm co-doping on the thermoluminescence (TL) and optically stimulated luminescence (OSL) properties of LiMgPO 4 :Tb,Sm,B through a combined approach of first-principles calculations and experimental validation. Theoretical computations reveal that the most stable doping configuration corresponds to Tb and Sm ions co-substituting at equivalent Mg sites, where mutual repulsive interactions lead to their spatial separation. Experimentally, samples with varying Tb/Sm concentrations were synthesized, and XRD results demonstrate no significant structural modifications upon doping, consistent with theoretical predictions. The TL glow curves exhibit first-order kinetics with characteristic peaks at 160 °C and 280 °C. The trap parameters including activation energy (E) and frequency factor (s) increase with rising dopant concentration, aligning with the localized behavior predicted by calculations, which arises from the repulsive interaction between Tb and Sm ions. The OSL performance reaches its optimum at 0.5 mol% Tb and 0.46 mol% Sm, beyond which concentration quenching occurs. This trend corroborates the theoretical mechanism wherein spatial separation at high dopant concentrations promotes energy migration, ultimately reducing luminescence efficiency. By integrating theoretical and experimental evidence, this work elucidates the microscopic mechanism through which dopant concentration regulates defect complex formation in Mg-based phosphors, providing a fundamental basis for designing high-performance radiation dosimeters.