Tetrahedron-based deep-ultraviolet nonlinear optical crystal with optimized KBe2BO3F2-like structure and disordered cations

On account of the development of deep-ultraviolet (DUV) nonlinear optical (NLO) crystals, tetrahedron-based compounds have attracted more and more attention, due to their large band gap. Thus, it is urgent to study a lot of these crystals for conducting structural optimization to achieve a balance of optical properties. Thus, this paper designs and obtains the Li2NH4Rb(SO4)(2) crystal, an alkali metal sulfate, which is composed of an optimized KBe2BO3F2-like structure and disordered Rb and [NH4] cations. It exhibits a strong second-harmonic generation (SHG) response of 2 x KH2PO4, a large band gap of 7.56 eV and a favorable growth habit to large crystals, simultaneously. Thus, the Li2NH4Rb(SO4)(2) crystal is a typical tetrahedron-based DUV NLO example. The coordination of the optimized KBe2BO3F2-like structure and the disordered cations results in the strong SHG response. This structural design strategy will facilitate the exploration of novel DUV NLO crystals.