Ba₄Ga₂B₈O₁₈Cl₂·NaCl: A New Polar Structure with NaCl Inclusion

The title compound, Ba4Ga2B8O18Cl2·NaCl, is found to crystallize in a polar space group P42nm with cell dimensions of a = 12.1134(2) Å and c = 6.8456(1) Å. The basic building blocks of the structure are the B4O9 groups, which are interconnected by the GaO4 tetrahedron to form a three-dimensional net with Ba2+ ion-, Cl- ion-, and NaCl molecule-filled tunnels. This net structure is closely related to that of mineral hilgardite, with which many variant compounds have been found. Both a powder second-harmonic-generation test and calculations suggest that it possesses an optical nonlinearity comparable to that of potassium dihydrogen phosphate.标题化合物Ba₄Ga₂B₈O₁₈Cl₂·NaCl结晶于极性空间群P42nm，晶胞参数为a=12.1134(2) Å，c=6.8456(1) Å。该结构的基本结构基元为B₄O₉基团，此类基团通过GaO₄四面体相互连接，构筑出三维网络结构，其中存在内嵌Ba²⁺离子、Cl⁻离子与NaCl分子的孔道。该网络结构与希尔加德石（hilgardite）的结构密切相关，目前已发现多种该矿物的结构变体化合物。粉末二次谐波发生测试与理论计算均表明，该化合物的光学非线性性能可与磷酸二氢钾（potassium dihydrogen phosphate）相媲美。