PbBeB 2 O 5 : A High-Performance Ultraviolet Nonlinear-Optical Crystal with Functional [BeB 2 O 8 ] 8- Group.

High-performance nonlinear-optical (NLO) crystals need to simultaneously meet multiple basic and conflicting performance requirements. Here, by using a partial chemical substitution strategy, the first noncentrosymmetric (NCS) PbBeB 2 O 5 crystal with a BeB 2 O 8 group was synthesized, exhibiting a two-dimensional [BeB 2 O 5 ] ∞ layer constructed by interconnecting BeB 2 O 8 groups and bridged PbO 4 with an active lone pair. The crystal shows a promising UV NLO functional feature, including a strong SHG effect of 3.5 × KDP (KH 2 PO 4 ), large birefringence realizing phase matchability in the whole transparency region from 246 to 2500 nm, a short UV absorption edge of 246 nm, and single-crystal easy growth. Remarkably, theoretical studies reveal that the BeB 2 O 8 group has high nonlinear activity, which could stimulate the discovery of a series of excellent NLO beryllium borates.