Variation of hydrogen bonded O···O distances in goethite at high pressure
Variation of hydrogen bonded O···O distances in goethite at high pressure
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DOI：
10.2138/am-2003-1005
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发表时间：
2003-10
影响因子：
3.1
通讯作者：
T. Nagai;H. Kagi;T. Yamanaka
中科院分区：
文献类型：
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作者：
T. Nagai;H. Kagi;T. Yamanaka
在日本光子工厂的BL-18C金刚石顶压室中，对针铁矿进行了高达24.5 Gpa的同步辐射X射线粉末原位衍射实验。针铁矿的压缩行为是各向异性的：靠近氢键方向的a轴的可压缩性几乎是b轴和c轴的两倍。用二阶Birch-Murnaghan方程(K‘=4)对单位晶胞体积和压力进行拟合，得到体积弹性系数K_0=111(2)GPA。压力介质对针铁矿的压缩行为有明显的影响，当压力超过11 GPa时，4：1的甲醇：乙醇压力介质会发生突然的应变展宽，此时会发生凝固。用Rietveld方法在10 Gpa以下的几个压力下对针铁矿的晶体结构进行了修正。主要压缩发生在晶体结构中的“空隙通道”，也就是OH···O桥所在的位置。氢键O···O距离随着压力的增加而缩短，约为-0.023？/Gpa，在9 Gpa时达到2.6(1)？
Abstract In-situ synchrotron X-ray powder diffraction experiments on goethite were performed up to 24.5 GPa using a diamond-anvil cell at BL-18C in the Photon Factory, Japan. The compression behavior of goethite is anisotropic: the a axis, which is close to the direction of the hydrogen bond, is almost twice as compressible as the b and c axes. A second-order Birch-Murnaghan fit (K' = 4) to the unitcell volumes and pressures up to 24 GPa gave a bulk modulus K0 = 111(2) GPa. The pressure medium apparently affects the compression behavior of goethite, as a sudden strain broadening occurs above 11 GPa, where solidification of the 4:1 methanol:ethanol pressure medium occurs. The crystal structure of goethite was refined by means of the Rietveld method at several pressures below 10 GPa. The main compression occurs in the “vacant channels” in the crystal structure, where the OH ···O bridges are located. The hydrogen-bonded O···O distance shortens with increasing pressure at the rate of about -0.023 Å/GPa and reaches 2.60(1) Å at 9 GPa.