Correlation of Internal Torsional Motion with Overall Molecular Motion in Crystals
Correlation of Internal Torsional Motion with Overall Molecular Motion in Crystals
复制标题
晶体中内部扭转运动与整体分子运动的相关性
DOI：
10.1107/s0108768198003243
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
K. Trueblood
中科院分区：
文献类型：
--
作者：
V. Schomaker;K. Trueblood
简单的单参数Dunitz-White模型的内部扭转运动伴随着整体分子运动在晶体中忽略了这种扭转和整体平移和天平动之间的相关性。这些相关性在这里被明确地考虑，在二次近似中（基于位移的线性近似）。对于每个附加刚性组（ARG）进行扭转天平动，有，除了均方天平动振幅，六个相关性要考虑，三个与整体分子天平动和三个与整体平移。因为从观察到的二次平均位移中不可能区分扭转运动和平行于扭转轴的整体分子天平动，所以本分析强调平行于扭转轴的整体天平动，我们称之为\Lambda。在一般情况下，每个ARG只有六个可确定的参数。如果ARG的扭转轴位于分子对称元素上，则参数的数量减少到三个或更少。包括这些相关性的分析的例子，没有他们，进行了比较。
The simple one-parameter Dunitz–White model for internal torsional motion accompanying overall molecular motion in crystals ignores the correlations between this torsion and the overall translation and libration. These correlations are explicitly considered here, in quadratic approximation (based on the linear approximation for displacements). For each attached rigid group (ARG) undergoing a torsional libration, there are, in addition to the mean-square libration amplitude, six correlations to be considered, three with the overall molecular libration and three with the overall translation. Because it is impossible from the observed quadratic mean displacements to distinguish the torsional motion from the overall molecular libration parallel to the torsional axis, the present analysis emphasizes the overall libration parallel to the torsional axis, which we term \Lambda. In the general case there are only six determinable parameters for each ARG. If the torsional axis of the ARG lies on a molecular symmetry element, the number of parameters is reduced to three or fewer. Examples of analyses with these correlations included, and without them, are compared.