The role of the inversion centre in texture analysis
The role of the inversion centre in texture analysis
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DOI：
10.1107/s0021889880012757
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发表时间：
1980-12
影响因子：
6.1
通讯作者：
H. Bunge;C. Esling;J. Muller
中科院分区：
文献类型：
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作者：
H. Bunge;C. Esling;J. Muller
非中心对称对映体材料的多晶样品可以被认为是由右手相和左手相组成的两相材料，其中每一个都具有其自己的织构。中心对称的晶体可以同时被认为是右旋或左旋的。如果要充分考虑晶体的右手和左手性质，那么统计样本对称性就可以用黑白点群而不是普通点群来描述。如果样品的对称性不属于一个“灰色”的群体，那么系列展开的纹理功能包含条款的奇数阶被涂抹在多晶衍射实验凭借反演中心的晶体对称性或弗里德尔定律。然而，在某些情况下，似乎可以通过利用纹理函数的零范围内的非负性条件来获得对奇数部分的近似。许多重要的物理性质都是中心对称的（即使晶体本身不是）。在这些情况下，织构函数的奇数部分不进入将多晶性质与相应的单晶相关联的表达式。
Polycrystalline samples of non-centrosymmetrical enantiomorphic materials may be considered as two-phase materials consisting of a right-handed and a left-handed phase, each of which has its own texture. Centrosymmetrical crystals may be considered as right- or left-handed at the same time. If the right- and left-handed nature of the crystals is fully to be taken into account then the statistical sample symmetry is correctly to be described by black–white point groups rather than by the ordinary ones. If the sample symmetry does not belong to one of the `grey' groups then the series expansion of the texture functions contains terms of odd order which are blotted out in polycrystal diffraction experiments by virtue of the inversion centre in the crystal symmetry or by Friedel's law. In certain cases it seems possible, however, to obtain an approximation to the odd part by making use of the non-negativity condition in the zero ranges of the texture function. Many important physical properties are centrosymmetric (even if the crystals themselves are not). In these cases the odd part of the texture function does not enter into the expression relating the polycrystal property to the corresponding one of the single crystals.