Deep-ultraviolet (deep-UV) nonlinear optical (NLO) crystals play a crucial role in modern laser frequency conversion technology. Traditionally, the exploration of deep-UV NLO crystals is mainly focused on borates, while, the use of phosphates recently opened up a novel and promising non-boron pathway for designing new deep-UV NLO crystals. Extending this pathway to aluminosilicates led to the discovery of Li3AlSiO5, the first NLO crystal in this system. It crystallizes in the polar space group Pna21 (no. 33) with a quaternary diamond-like structure composed of LiO4, AlO4 and SiO4 tetrahedral groups. The compound exhibits a deep-UV cut-off edge below 190 nm and is phase matchable with moderate powder second harmonic generation (SHG) intensity (0.8KH2PO4). The band gap calculated using PBE0 is 7.29 eV, indicating that the cut-off edge of the Li3AlSiO5 crystal can be down to 170 nm. In addition, the compound is nonhygroscopic and thermally stable up to ∼1472 K. These results suggest that Li3AlSiO5 is a potential deep-UV NLO crystal. First-principles studies were performed to elucidate the structure-property relationship of Li3AlSiO5.

A new centrosymmetric alkaline-earth metal borate, Ba2B10O17, has been successfully synthesized through high-temperature solid-state reactions. The single-crystal X-ray structural analysis shows that Ba2B10O17 crystallizes in the triclinic space group P1[combining macron]. The parameters of the triclinic unit cell are a = 6.7128(3) Å, b = 9.8698(4) Å, c = 9.9998(4) Å, α = 76.860(3)°, β = 83.200(3)°, γ = 73.332(3)°, and Z = 2. The title compound features a [B10O17]∞ three-dimensional anionic framework with infinite channels in which the Ba(2+) cations are located. Ba2B10O17 possesses a large experimental band gap of 6.29 eV and a short cut-off edge lower than 180 nm proved by the transmission spectrum on a single crystal sample 0.5 mm in thickness. The calculated band structures and the density of states of Ba2B10O17 suggest that its indirect energy gap is 5.97 eV which agrees with the experimental result. The thermal behavior and the IR spectrum of Ba2B10O17 are also reported in this work.