Yoo Chung Yul, Hong Kun Pyo, Kim Seung Joo
Department of Chemistry, Division of Energy Systems Research, Ajou University, Suwon 443-749, Republic of Korea.
Acta Crystallogr C. 2007 Aug;63(Pt 8):i63-5. doi: 10.1107/S0108270107029563. Epub 2007 Jul 14.
The structure of a new layered oxyfluoride, viz. potassium strontium diniobium hexaoxide fluoride, KSrNb(2)O(6)F, was refined from powder neutron diffraction data in the orthorhombic space group Immm. The oxyfluoride compound is an n = 2 member of the Dion-Jacobson-type family of general formula A[A'(n-1)B(n)X(3n+1)], which consists of double layered perovskite slabs, SrNb(2)O(6)F, between which K(+) ions are located. Within the perovskite slabs, the NbO(5)F octahedra are significantly distorted and tilted about the a axis. A bond-valence-sum calculation gives evidence for O/F ordering in KSrNb(2)O(6)F, with the F(-) ions located in the central sites of the corner-sharing NbO(5)F octahedra along the b axis. All atoms lie on special positions, namely Nb on m, Sr on mmm, K on m2m, F on mm2, and O on sites of symmetry m and m2m.
一种新型层状氟氧化物，即氟氧化钾锶二铌（KSrNb₂O₆F）的结构，通过粉末中子衍射数据在正交空间群Immm中进行了精修。该氟氧化物化合物是通式为A[A'(n - 1)BₙX₃ₙ₊₁]的Dion - Jacobson型家族的n = 2成员，它由双层钙钛矿板[SrNb₂O₆F]⁻组成，K⁺离子位于这些双层之间。在钙钛矿板内，NbO₅F八面体明显扭曲并围绕a轴倾斜。键价和计算为KSrNb₂O₆F中的O/F有序排列提供了证据，F⁻离子沿着b轴位于共角NbO₅F八面体的中心位置。所有原子都处于特殊位置，即Nb位于m位置，Sr位于mmm位置，K位于m2m位置，F位于mm2位置，O位于对称m和m2m的位置。
