Exploring a new short-wavelength nonlinear optical fluoride material featuring unprecedented polar cis -[Zr 6 F 34 ] 10- 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 8 dodecahedron shows large polarizability anisotropy and benefits for large birefringence. Herein, a new fluorine-rich fluoride, K 3 Ba 2 Zr 6 F 31 , was synthesized by coupling the ZrF 8 group, featuring acentric cis -[Zr 6 F 34 ] 10- clusters with a 6 3 -screw axis. Significantly, K 3 Ba 2 Zr 6 F 31 exhibits a short UV cutoff edge (below 200 nm) and moderate second-harmonic generation (SHG) response (0.5 × KH 2 PO 4 ). 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 cis -[Zr 6 F 34 ] 10- cluster built by ZrF 8 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.