Obtaining compounds with large nonlinear-optical (NLO) coefficients and wide band gaps is challenging due to their competitive requirements for chemical bonds. Herein, the first member with mixed cations on the A site in the A-M₃-Q₅ or A-Ag-M₆-Q₁₀ (A = alkali metal; M = Ga, In; Q = S, Se, Te) family, viz. Na_0.45Ag_0.55Ga₃Se₅ (NAGSe), was obtained by a solid-state reaction. Its structure features [GaSe₄] tetrahedra built three-dimensional {[Ga₃Se₅]⁻}_∞ network, with Na and Na/Ag cations located at the octahedral cavities. Noncentrosymmetric (R32) NAGSe can also be transformed from centrosymmetric RbGa₃S₅ (P2₁/c) via multiple-site cosubstitution. NAGSe exhibits the highest NLO response (1.9 × AGS) in the A-Ag-M-Q family. Crystal structure analysis and theoretical calculations suggest that the NLO response is mainly contributed by the regularly arranged [GaSe₄] units. This work enriches the exploration of the undeveloped A-M₃-Q₅ or A-Ag-M₆-Q₁₀ family as potential infrared NLO materials.

中文翻译：

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多取代诱导的中心对称到非中心对称结构转变和非线性光学行为：Na0.45Ag0.55Ga3Se5 的案例

由于对化学键的竞争性要求，获得具有大非线性光学（NLO）系数和宽带隙的化合物具有挑战性。在此，AM ₃ -Q ₅或 A-Ag-M ₆ -Q ₁₀ (A = 碱金属；M = Ga、In；Q = S、Se、Te) 族中 A 位上具有混合阳离子的第一个成员，即。通过固相反应得到Na _0.45 Ag _0.55 Ga ₃ Se ₅ (NAGSe)。其结构特点是[GaSe ₄ ]四面体构建了三维{[Ga ₃ Se ₅ ] ⁻ } _∞网络，Na和Na/Ag阳离子位于八面体空腔内。非中心对称( R 32 ) NAGSe 也可以通过多位点共取代从中心对称RbGa ₃ S ₅ ( P 2 ₁ / c )转化。 NAGSe 在 A-Ag-MQ 系列中表现出最高的 NLO 响应 (1.9 × AGS)。晶体结构分析和理论计算表明，非线性光学响应主要由规则排列的[GaSe ₄ ]单元贡献。这项工作丰富了对未开发的 AM ₃ -Q ₅或 A-Ag-M ₆ -Q ₁₀家族作为潜在红外 NLO 材料的探索。