AZn(PO3)3 (A = K, Rb): Deep-Ultraviolet Nonlinear Optical Phosphates Derived from Synergy of a Unique [ZnO6] Octahedron and a [PO3]∞ Chain

Deep-ultraviolet (deep-UV) nonlinear optical (NLO) phosphates have become a continuing hot spot since the discovery of Ba3P3O10X. Herein, we report two new deep-UV NLO phosphates, KZn(PO3)3 and RbZn(PO3)3, crystallizing in the asymmetric R3 (No. 146) space group with a three-dimensional (3D) network constructed by [PO3]∞ chains and distorted C3v [ZnO6] octahedra. Both compounds exhibit phase-matchable behaviors with relatively strong powder SHG intensities (about 0.6× and 0.7× those of the benchmark KDP) and short deep-UV cutoff edges (<200 nm). First-principles calculations reveal the synergy of the distorted [ZnO6] octahedron and the flexible [PO3]∞ chain that contribute respectively to the d16 value by 14 and 84% in KZn(PO3)3 or 6 and 93% in RbZn(PO3)3. Remarkably, the SHG-active [ZnO6] herein is pointed out for the first time, which offers an unconventional access to the design and searches for deep-UV NLO material candidates.