Centric Sc(HPO 3 )(H 2 PO 3 )(H 2 O) and Acentric Sc(H 2 PO 3 ) 3 : 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 3 )(H 2 PO 3 )(H 2 O) and Sc(H 2 PO 3 ) 3 , were successfully synthesized. Centric Sc(HPO 3 )(H 2 PO 3 )(H 2 O) exhibits a short UV cutoff edge (<200 nm) and a unique double-layer structure of [Sc 2 (HPO 3 ) 2 (H 2 PO 3 ) 2 (H 2 O) 2 ] ∞ . The acentric Sc(H 2 PO 3 ) 3 exhibits a three-dimensional [Sc(H 2 PO 3 ) 3 ] ∞ structure with a large band gap of 4.05 eV, and it demonstrates a moderately phase-matchable second-harmonic-generation response [0.60 × KDP (KH 2 PO 4 )] 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.