标题： 非晶态锗氧化物和二氧化硅中的键角分布 显示英文标题

标题： Bond angle distribution in amorphous germania and silica

摘要： 非晶态二氧化锗和二氧化硅中Ge-O-Ge和Si-O-Si键角alpha的分布是基于衍射实验重新确定的。 连接相邻四面体的键角alpha是这些玻璃任何连续随机网络描述（CRN）中的核心参数。 本文介绍了对非晶态二氧化锗在光子能量为97和149 keV条件下的高能光子衍射实验，覆盖动量转移范围为0.6-33.5 AA^{-1}。 在GeO2的光子衍射实验中，OO对的贡献非常小。 为了获得非晶态SiO2的类似信息，高能光子衍射实验与非晶态二氧化硅的中子衍射数据相结合，以消除OO-部分结构因子。 通过这种技术表明，Si-O-Si角度分布较窄（sigma=7.5度），实际上其宽度与Ge-O-Ge角度分布（sigma=8.3度）相当，这一结果与当前观点不同。 本研究发现的更窄分布与基于29Si-MAS-NMR的测定结果更加一致。 在各种将化学位移与键角相关联的模型中，与基于正切模型的模型最为吻合。 在达到的实空间分辨率0.09 AA内，可以排除键角分布中的尖锐成分。 显示英文摘要

摘要： The distribution of Ge-O-Ge and Si-O-Si bond angles alpha in amorphous germania and silica is re-determined on the basis of diffraction experiments. The bond angle alpha joining adjacent tetrahedra is the central parameter of any continuous random network description (CRN) of these glasses. New high energy photon diffraction experiments on amorphous germania (at photon energies of 97 and 149 keV) are presented, covering the momentum transfer 0.6-33.5 AA^{-1}. In photon diffraction experiments on GeO2 the contribution of the OO pairs is very small. To obtain a similar information for amorphous SiO2, high energy photon diffraction experiments have been combined with neutron diffraction data on amorphous silica in order to eliminate the OO- partial structure factor. With this technique it is shown that the Si-O-Si angle distribution is fairly narrow (sigma=7.5 degree) and in fact comparable in width to the Ge-O-Ge angle distribution (sigma=8.3 degree), a result which differs from current opinion. The narrower distribution found in this study are in much better agreement to the determinations based on 29Si-MAS-NMR. Among the various models relating the chemical shift to the bond angle, best agreement is found with those models based on the secant model. Sharp components in the bond angle distribution can be excluded within the reached real space resolution of 0.09 AA.