查看完整版本: 请教：单晶，单重孪晶，多重孪晶的区别。

请教：单晶，单重孪晶，多重孪晶的区别。

在看文献的过程中，越来越迷惑，单晶、孪晶和晶面的生长有什么关系吗？越看越不知道该如何区分单晶和孪晶了，希望大家给与指点一下。文献见[url]http://www.nanost.net/bbs/viewthread.php?tid=14286[/url]。jMR9b^V3f
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一般把twinning翻译为“孪晶”。孪晶是指按一定取向规律相邻排列的两个（或多个）晶体，可以利用一个对称操作使其中的一个晶体与另一个晶体重复。使两个晶体重复的对称操作可以是点对称旋转操作，如绕某一点阵方向旋转60、90、120或180度，或通过某一点阵平面的镜面反映，也可以是微观对称操作，如镜面反映滑移和螺旋轴。F*DXY7f)g8P

#z[6e qTI4X| 孪晶的种类（按结构）：7Nq^
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由绕某一点阵方向的旋转对称操作形成的孪晶结构称为旋转孪晶；+g'TF6D^;i N
由通过某一点阵平面的镜面反映对称操作形成的孪晶结构称为反映孪晶；6P@Z_O
有孪晶取向关系的两个晶体在一个局部区域重复出现时称为多重孪晶。
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[b]Crystal twinning[/b] from Wikipedia.3{#E|V$Gfi1DH)n

4i2Sz9Pi Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals. Crystallographers classify twinned crystals by a number of twin laws. These twin laws are specific to the crystal system. The type of twinning can be a diagnostic tool in mineral identification.
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}0P2roA];p.F1r Simple twinned crystals may be contact twins or penetration twins. Contact twins share a single composition surface often appearing as mirror images across the boundary. Quartz, gypsum, and spinel often exhibit contact twinning. In penetration twins the individual crystals have the appearance of passing through each other in a symmetrical manner. Orthoclase, staurolite, pyrite, and fluorite often show penetration twinning.D'g V4FO^{&T

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b [&[Al#i If several twin crystal parts are aligned by the same twin law they are referred to as multiple or repeated twins. If these multiple twins are aligned in parallel they are called polysynthetic twins. When the multiple twins are not parallel they are cyclic twins. Albite, calcite, and pyrite often show polysynthetic twinning. Closely spaced polysynthetic twinning is often observed as striations or fine parallel lines on the crystal face. Rutile, aragonite, cerussite, and chrysoberyl often exhibit cyclic twinning, typically in a radiating pattern.
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There are three modes of formation of twinned crystals. Growth twins are the result of an interruption or change in the lattice during formation or growth due to a possible deformation from a larger substituting ion. Annealing or Transformation twins are the result of a change in crystal system during cooling as one form becomes unstable and the crystal structure must re-organize or transform into another more stable form. Deformation or gliding twins are the result of stress on the crystal after the crystal has formed. Deformation twinning is a common result of regional metamorphism.+t'NX w"u

6b7HXA$@1xe(p Of the three common crystal structures: BCC, FCC, and HCP, the HCP structure is the most likely to twin.U/H6V9v
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Crystals that grow adjacent to each other may be aligned to resemble twinning. This parallel growth simply reduces system energy and is not twinning.3@0@bw~Z3vp7k!a

k3Zj.d$Y3e\\L L More information about crystallography pls visit:
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