Silicogermanate Ba 2 K 2 In 2 [(Si 0.8 Ge 0.2 ) 6 O 18 ] · 2H 2 O As an Analogue of the Natural Zirconosilicate Kostylevite K 4 Zr 2 [Si 6 O 18 ] · 2H 2 O

Crystals of new silicogermanate Ba 2 K 2 In 2 [(Si 0.8 Ge 0.2 ) 6 O 18 ] · 2H 2 O were prepared by the hydrothermal synthesis; sp. gr. P 2 1 / n , a = 6.5548(6) Å, b = 11.6946(10) Å, c = 13.0203(11) Å, β = 102.774(1)°. This compound is structurally similar to the natural zirconosilicate kostylevite K 4 Zr 2 [Si 6 O 18 ] · 2H 2 O (sp. gr. P 2 1 / c ), in which Zr atoms are replaced by In atoms, K atoms are partially replaced by Ba atoms, and Ge atoms are isomorphously incorporated into SiO 4 tetrahedra. The six-membered tetrahedral rings composed of (Si,Ge)O 4 tetrahedra are linked by InO 6 octahedra to form a mixed framework, with large cations located in the cavities. The difference in the space group designation is only in the choice of the coordinate axes and, correspondingly, in the setting of the same monoclinic space group.