1：Experimental Design and Method Selection:

The study employed synergistic combination strategy to design a new compound. Polycrystalline samples were synthesized via solid-state reaction, and single crystals were grown using the top seeded solution growth (TSSG) method. Theoretical calculations using density functional theory (DFT) with CASTEP package were performed to predict optical properties.

2：Sample Selection and Data Sources:

Precursors included Li2CO3, Na2CO3, and H3BO3 from Aladdin. Crystal structure data were obtained from X-ray diffraction (XRD) measurements.

3：List of Experimental Equipment and Materials:

Equipment included aurum crucibles, programmable temperature electric furnace, NETZSCH STA 449C thermal analyzer, Bruker D2 PHASER diffractometer, Bruker SMART APEX II CCD diffractometer, Metricon model 2010/M prism coupler, Shimadzu SolidSpec-3700DUV spectrophotometer, Dandong YX-2 X-ray orientator, and Q-switched Nd:YAG laser. Materials were Li2CO3 (Aladdin, 99.5%), Na2CO3 (Aladdin, 99.5%), H3BO3 (Aladdin, 99.8%).

4：5%), Na2CO3 (Aladdin, 5%), H3BO3 (Aladdin, 8%). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Polycrystalline synthesis involved heating mixtures to 550°C for 72h. Crystal growth used TSSG with a cooling rate of 0.2°C/d. Thermal analysis was conducted with TG-DSC. Refractive indices were measured at specific wavelengths. UV-Vis-NIR transmission spectra and laser-induced damage tests were performed.

5：2h. Crystal growth used TSSG with a cooling rate of 2°C/d. Thermal analysis was conducted with TG-DSC. Refractive indices were measured at specific wavelengths. UV-Vis-NIR transmission spectra and laser-induced damage tests were performed. Data Analysis Methods:

5. Data Analysis Methods: XRD data were integrated with SAINT and refined with SHELXTL. Refractive indices were fitted to Sellmeier equations. DFT calculations used PBE functional with GGA and NCP pseudopotentials.