Prediction of Promising Deep Ultraviolet Nonlinear Optical Materials in the Li2O–B2O3 System

Abstract

Deep ultraviolet (UV) nonlinear optical (NLO) materials are of intense interest owing to their broad technological applications from laser photolithography to semiconductor manufacturing, biomedicine, and attosecond pulse generation. To date, deep UV NLO materials are still scarce due to the multiple rigorous criteria that should be fulfilled. Using evolutionary crystal structure prediction combined with first-principles calculations, we systematically explored the pseudobinary Li2O–B2O3 system and predicted twenty-four metastable structures in the Li2O–B2O3 system. We found that four structures of LiBO2, e.g., oC16, oP16-1, oP16-2, and mP16, are promising deep UV NLO crystals. Among them, oC16-LiBO2, oP16-2-LiBO2, and mP16-LiBO2 exhibit significantly large SHG coefficients (>6 KDP), moderate birefringence (∼0.12@1064 nm), and suitable band gaps (∼7 eV). Importantly, the oC16-LiBO2 structure is expected to be synthesized experimentally as its formation energy is lower than that of γ-LiBO2.