A Rare‐Earth Selenite with Unexpectedly Well‐Balanced Ultraviolet Nonlinear Optical Functionality, Sc(HSeO3)3

Establishing high performance ultraviolet (UV) nonlinear optical (NLO) selenite crystals with well-balanced properties is very challenging attributable to their strong absorption for UV light. Here a rare-earth selenite, Sc(HSeO3 )3 , with excellent UV NLO properties is introduced. Sc(HSeO3 )3 crystallizing in the polar NCS space group, Cc, features a 3D archetiture built up by interconnected ScO6 octahedra and HSeO3 groups. The crystal exhibits remarkably well-balanced UV-NLO functionality, namely, the shortest absorption edge (214 nm) among NLO-active selenites, wide bandgap (5.28 eV), large phase-matchable SHG response (5 × KDP), and sufficiently large birefringence (cal. 0.105 @1064 nm). Detailed DFT calculations have been performed to elucidate the structure-property relationships. This work provides a new example of discovering novel UV NLO selenite materials.