Neutron diffraction study of δ-AlOOD at high pressure and its implication for symmetrization of the hydrogen bond
Neutron diffraction study of δ-AlOOD at high pressure and its implication for symmetrization of the hydrogen bond
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DOI：
10.2138/am.2008.2849
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发表时间：
2008-10-01
影响因子：
3.1
通讯作者：
Ohtani, Eiji
中科院分区：
文献类型：
--
作者：
Sano-Furukawa, Asami;Komatsu, Kazuki;Ohtani, Eiji
我们在高达9.2 GPa的压力下对扭曲的金红石型水合相delta-AlOO（D0.74H0.26）进行了粉末中子衍射研究。Rietveld精修表明，所观察到的衍射数据是最好的拟合模型与不对称氢键（空间群P2（1）nm）。AlO 6八面体的Al-O-2键保持比Al-O 1键长，直到9.2GPa，反映了O2是O2-D中心点中心点O 1的氢键的供体而O 1是受体的事实。随着压力的增加，Al-O 1键长几乎保持不变或略有增加，而较长的Al-O2键更可压缩。八面体的共享边缘的O中心点O距离几乎是恒定的，不像在压缩期间减小的其他O中心点O距离。AlO 6八面体的体积模量被确定为197.0（4）GPa，其中K'被固定为4。AlO 6八面体在压缩到9.2 GPa期间旋转约1度。随着压力增加和O2中心点中心点O 1距离减小，D中心点中心点O 1键缩短，而O2-D键变长，压力依赖性分别为-1.81（9）× 10（-2）埃/GPa和0.57（8）× 10（-2）埃/GPa，这意味着高压下氢键的对称化。随着压力的增加，120反射的强度减小，这表明在高压下，在δ-AlOOD中将发生从空间群P2（1）nm到Pnnm的结构转变。这种转变可能是由于氘的无序或氢键的对称化。
We have conducted a powder neutron diffraction study of the distorted rutile-type hydrous phase delta-AlOO(D0.74H0.26) at pressures up to 9.2 GPa. Rietveld refinement reveals that the observed diffraction data are best fitted by a model with an asymmetric hydrogen bond (space group P2(1)nm). The Al-O-2 bonds of the AlO6 octahedron remain longer than the Al-O1 bonds up to 9.2 GPa, reflecting the fact that O2 is the donor and O1 is the acceptor of the hydrogen bond of O2-D center dot center dot center dot O1. As pressure increases, the Al-O1 bond lengths remain almost constant or increase slightly, whereas the longer Al-O2 bonds are more compressible. The O center dot center dot center dot O distance of the shared edge of the octahedron is almost constant unlike the other O center dot center dot center dot O distances that decrease during compression. The bulk modulus of the AlO6 octahedron is determined to be 197.0(4) GPa, where K' is fixed to 4. The AlO6 octahedron rotates about 1 degrees during compression to 9.2 GPa. As pressure increases and the O2 center dot center dot center dot O1 distance decreases, the D center dot center dot center dot O1 bond is shortened, whereas the O2-D bond becomes elongated, with pressure dependencies of-1.81(9) x 10(-2) angstrom/GPa and 0.57(8) x 10(-2) angstrom/GPa, respectively, implying the symmetrization of the hydrogen bond at high pressure. The decrease in intensity of the 120 reflection as pressure increases suggests that the transition from the structure with space group P2(1)nm to that with Pnnm would take place in delta-AlOOD at high pressure. This transition could be attributed to the disorder of deuterium or symmetrization of the hydrogen bond.