From centrosymmetric to noncentrosymmetric: cation-directed structural evolution in X3ZnB5O10 (X = Na, K, Rb) and Cs12Zn4(B5O10)4 crystals

Abstract

A new deep-ultraviolet nonlinear optical crystal, Cs₁₂Zn₄(B₅O₁₀)₄, was synthesized via a high temperature solution method. The crystal structure was solved in the noncentrosymmetric space group (Cc, no. 9). Owing to the cation size effect, from X₃ZnB₅O₁₀ (X = Na, K, and Rb) to Cs₁₂Zn₄(B₅O₁₀)₄, the structure changes from centrosymmetric to noncentrosymmetric. Cs₁₂Zn₄(B₅O₁₀)₄ exhibits a 3D [ZnB₅O₁₀]_∞ network, however, X₃ZnB₅O₁₀ (X = Na, K, and Rb) exhibits a 2D [ZnB₅O₁₀]_∞ layer. It is worth mentioning that Cs₁₂Zn₄(B₅O₁₀)₄ displays a short cutoff edge (below 185 nm), which is remarkable among the reported Zn-containing NLO crystals. Meanwhile, the compound exhibits a moderate SHG response and melts congruently. In addition, the relationship between its structure and NLO properties was also discussed in detail using the density functional theory (DFT) method.