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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Motion in Crystals: The Molecular Mean Field Model
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Motion in Crystals: The Molecular Mean Field Model

机译:晶体中的运动:分子均值场模型

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摘要

The problem of describing collective atomic motion in molecular crystals is reviewed from the point of view of normal coordinate analysis in its mean square amplitude form. There are two related problems with this approach: (1) The apparent lack of information on correlation between atomic motion inherent in atomic displacement parameters as determined from elastic diffraction experiments. (2) The need to identify molecular deformation coordinates associated with low frequencies and therefore with large amplitudes. Within the limits of the harmonic approximation the first problem can be solved by considering mean square amplitudes obtained at different temperatures. The second problem can be approached by analyzing and visualizing the deviations of atomic displacement parameters from rigid body behavior or, alternatively, by looking for static deformations of molecular fragments closely related in structure to the molecule whose atomic displacement parameters are to be analyzed. Some of the above points are illustrated with the help of the atomic displacement parameters of H8Si80I2, determined at 100 and 10 K.
机译:从正态坐标分析的均方振幅形式的角度回顾了描述分子晶体中集体原子运动的问题。这种方法有两个相关的问题:(1)显然缺乏有关由弹性衍射实验确定的原子位移参数中固有的原子运动之间的相关性的信息。 (2)需要识别与低频相关的分子变形坐标,因此振幅较大。在谐波近似的范围内,可以通过考虑在不同温度下获得的均方振幅来解决第一个问题。第二个问题可以通过分析和可视化原子位移参数与刚体行为的偏差来解决,或者通过寻找结构上与要分析其原子位移参数的分子密切相关的分子片段的静态变形来解决。在H8Si80I2的原子位移参数(确定为100和10 K)的帮助下,说明了上述几点。

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