Exploring a new short-wavelength nonlinear optical fluoride material featuring unprecedented polar -[ZrF] clusters.

Traditional fluorides are rarely reported as candidates for nonlinear optical (NLO) materials featuring a deep-ultraviolet cutoff edge. Theoretical investigations suggest that the ZrF dodecahedron shows large polarizability anisotropy and benefits for large birefringence. Herein, a new fluorine-rich fluoride, KBaZrF, was synthesized by coupling the ZrF group, featuring acentric -[ZrF] clusters with a 6-screw axis. Significantly, KBaZrF exhibits a short UV cutoff edge (below 200 nm) and moderate second-harmonic generation (SHG) response (0.5 × KHPO). It also possesses a relatively large birefringence (0.08@1064 nm), together with a broad transparency window (2.5-21.1 μm). First-principles calculations suggest that the -[ZrF] cluster built by ZrF dodecahedra are the dominant contributors to the large band gap (7.89 eV, cal.) and SHG response simultaneously. Such systematic work highlights that Zr-based fluorides afford a new paradigm for the development of efficient NLO materials with a short UV cutoff edge.