Centric Sc(HPO)(HPO)(HO) and Acentric Sc(HPO): Two Ultraviolet Scandium Phosphite Optical Crystals.

Exploring ultraviolet (UV) nonlinear-optical (NLO) materials is significant for the conversion of a high-frequency laser. Two scandium phosphites, Sc(HPO)(HPO)(HO) and Sc(HPO), were successfully synthesized. Centric Sc(HPO)(HPO)(HO) exhibits a short UV cutoff edge (<200 nm) and a unique double-layer structure of [Sc(HPO)(HPO)(HO)]. The acentric Sc(HPO) exhibits a three-dimensional [Sc(HPO)] structure with a large band gap of 4.05 eV, and it demonstrates a moderately phase-matchable second-harmonic-generation response [0.60 × KDP (KHPO)] at 1064 nm. The crystal structures, optical properties, and theoretical calculations of the two compounds are discussed. This work will promote the exploration of new NLO phosphite materials.