Többens Daniel M, Kahlenberg Volker, Kaindl Reinhard
Institute of Mineralogy and Petrography, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria.
Inorg Chem. 2005 Dec 12;44(25):9554-60. doi: 10.1021/ic051401o.
The crystal structure of a sodium yttrium silicate with composition NaYSi2O6 has been determined from laboratory X-ray powder diffraction data by simulated annealing, and has been subsequently refined with the Rietveld technique. The compound is monoclinic with space group P2(1)/c and unit cell parameters of a=5.40787(2) A, b=13.69784(5) A, c=7.58431(3) A, and beta=109.9140(3) degrees at 23.5 degrees C (Z=4). The structure was found to be a single-chain silicate with a chain periodicity of four. The two symmetry dependent [Si4O12] chains in the unit cell are parallel to c. A prominent feature is the strong folding of the crankshaft-like chains within the b,c-plane resulting in intrachain Si-Si-Si angles close to 90 degrees. The coordination of the Y3+ ions by O2- is 7-fold in the form of slightly irregular pentagonal bipyramids, with oxygen atoms from four different chains contributing to the coordination polyhedron. Na+ ions are irregularly coordinated by 10 oxygens from two neighboring chains. No disorder of Na+ and Y3+ between the two nontetrahedral cation sites could be observed. Furthermore, micro-Raman spectra have been obtained from the polycrystalline material.
通过模拟退火从实验室X射线粉末衍射数据确定了组成为NaYSi₂O₆的硅酸钠钇的晶体结构，随后用Rietveld技术进行了精修。该化合物为单斜晶系，空间群为P2(1)/c，在23.5℃时晶胞参数为a = 5.40787(2) Å、b = 13.69784(5) Å、c = 7.58431(3) Å，β = 109.9140(3)°（Z = 4）。发现该结构是一种链周期为4的单链硅酸盐。晶胞中两个对称相关的[Si₄O₁₂]链平行于c轴。一个显著特征是在b、c平面内曲轴状链的强烈折叠，导致链内Si-Si-Si角接近90°。Y³⁺离子由O²⁻以略微不规则的五角双锥形式进行7配位，配位多面体中有来自四条不同链的氧原子。Na⁺离子由来自两条相邻链的10个氧原子进行不规则配位。未观察到Na⁺和Y³⁺在两个非四面体阳离子位点之间的无序现象。此外，还获得了该多晶材料的显微拉曼光谱。
