Module-Analysis-Assisted Design of Deep Ultraviolet Fluorooxoborates with Extremely Large Gap and High Structural Stability

The diversity of potential structures and the competition of material functionalities make material design still a big challenge. Here, we use down-to-top design by screening functional modules to realize targeted design of deep ultraviolet (DUV, <200 nm) nonlinear optical (NLO) materials. By adjusting boron–oxygen–fluorine configurations, we analyze the functional modules that can balance the competition between the UV transmittance and the second harmonic generation response, two key functionalities in the DUV region. Among these units, the BO3F module is screened as the optimal module with both large energy gap and second-order microscopic susceptibility. As a demonstration, we introduce the BO3F module to Sr2Be2B2O7, an excellent NLO material suffering from instability. The calculation results indicate that this introduction not only eliminates instability issue but show that the artificial compounds all have the shortest DUV cutoff edge in the commercial borate systems. Compared with that of KBe2BO3F2, the sole crystal used to produce DUV, their cutoff edges have about 20 nm blue shift.