Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9.
Octahedral tilting in the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9.
复制标题
极六方钨青铜 RbNbW2O9 和 KNbW2O9 中的八面体倾斜。
DOI：
10.1107/s2052520619009260
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
F. Morrison
中科院分区：
文献类型：
--
作者：
J. A. McNulty;A. Gibbs;P. Lightfoot;F. Morrison
用高分辨粉末中子衍射法测定了极性六方钨青铜RbNbW2O9和KNbW2O9的室温结构(正交晶系，Cmc21空间群)。在KNbW2O9中，A位阳离子沿c轴发生位移，并伴随着八面体倾斜，从而优化了A阳离子的成键环境，从而使配位数从18减少到16。这一影响在KNbW2O9中更为明显，因为A阳离子尺寸减小。这两个组分中的八面体倾斜导致c轴翻倍，这是以前从未报道过的，突显了中子衍射作为确定这类系统结构的补充技术的重要性。
The ambient-temperature structures (orthorhombic, space group Cmc21) of the polar hexagonal tungsten bronzes RbNbW2O9 and KNbW2O9 have been determined by high-resolution powder neutron diffraction. Displacement of the A-site cation along the polar c axis with concomitant octahedral tilting occurs to optimize the A cation bonding environment, hence reducing the coordination from 18 to 16. This effect is more evident in KNbW2O9 due to decreased A cation size. The octahedral tilting in both compositions results in a doubling of the c axis that has not previously been reported, highlighting the importance of neutron diffraction as a complementary technique for structural determination of such systems.