Prediction of new functional fluorooxoborates with expected anionic framework: a case of CaB₃O₅F

The prediction of new fluorooxoborates as ultraviolet (UV)/deep ultraviolet (DUV) opto-electronic functional materials from a largely unexplored chemical space is a challenging task. It has been suggested that the anionic frameworks formed by B-O and B-O-F units significantly influence on the physical properties of fluorooxoborates. Therefore, the rational design of anionic frameworks could facilitate the materials discovery process. Herein, we propose that a candidate anionic framework can be efficiently derived from an existing one by slightly altering its oxygen content. Following this idea, we hypothesized the existence of a 1D B₃O₅F_∞ chain from the well-known 2D B₆O₉F_2∞ layer. Accordingly, seven CaB₃O₅F structures with the expected anionic framework were successfully predicted. First-principles calculations show that all these structures have potential in the UV/DUV birefringent or nonlinear optical (NLO) material field, indicating that the 1D B₃O₅F_∞ chain is indeed a promising anionic framework for achieving UV/DUV birefringent and NLO performance.