The (3 + 1)-dimensional superspace description of the commensurately modulated structure of p-chlorobenzamide (α-form) and its relation to the γ-form
The (3 + 1)-dimensional superspace description of the commensurately modulated structure of p-chlorobenzamide (α-form) and its relation to the γ-form
复制标题
对氯苯甲酰胺（α型）等量调制结构的（3 + 1）维超空间描述及其与γ型的关系
DOI：
10.1524/zkri.218.7.507.20713
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
Gervais Chapuis
中科院分区：
文献类型：
--
作者：
A. Schönleber;P. Pattison;Gervais Chapuis
有机化合物对氯苯甲酰胺C7 H6 ClNO的室温结构（α-型）既可以描述为经典的三维周期超结构（αS），也可以描述为（3 + 1）维超空间中的周期调制结构（αM）。衍射图案的特征是主反射和卫星反射之间的强度明显不同。所有的反射都可以在三斜晶胞中用四个折射率hklm和超空间群P1 <$（αβγ）中的一个调制矢量来索引，其中调制矢量q <$= 1/3·a <$*。该结构在较高温度下经历相变。在该相变中，调制消失，如卫星反射的消失所指示的。所得高温相（γ-型）在不对称单元中含有一个分子，空间群为P1 π。高温结构（γ）非常接近室温下调制模型的参考结构。因此，相变可以理解为在高温下调制的损失。
Abstract The room temperature structure (α-form) of the organic compound p-chlorobenzamide, C7H6ClNO, can be described as a classical three-dimensional periodic superstructure (αS) and also as a commensurately modulated structure (αM) in (3 + 1)-dimensional superspace. The diffraction pattern is characterized by a clear difference in intensity between main and satellite reflections. All reflections can be indexed with four indices hklm in a triclinic unit cell and one modulation vector in the superspace group P1̅(αβγ) with the modulation vector q⃗ = 1/3·a⃗*. The structure undergoes a phase transition at higher temperature. In this phase transition the modulation vanishes as indicated by the disappearance of the satellite reflections. The resulting high temperature phase (γ-form) contains one molecule in the asymmetric unit, the space group is P1̅. The high temperature structure (γ) is very close to the reference structure of the modulated model at room temperature. The phase transition can therefore be understood as a loss of the modulation at high temperature.