(1) crystal structure can only exist 1,2,3,4 and 6 times the axis of symmetry, (2) can only have 14 kinds of space lattice form. n times the basic rotational operation of the rotation axis of symmetry 360 ° / n, and therefore, the symmetry of the crystal can be reflected in the shape of the shaft and macro only limited axle. Because atoms are not at rest, there is a lattice distortion caused by foreign atoms and certain defects, although the basic structure of the crystal is still in line with the above rules, but by no means as envisaged intact, there are different numbers of the various forms of defects. It also must be noted that the vast majority of industrial use of the metal material is not only constituted by a large single crystal, but by a large number of small crystals, i.e. polycrystal. Material inside the block, each small crystals (or grains) is separated from its neighbors throughout the three-dimensional space by the interface. This interface is called the grain boundary, called grain boundaries. The thickness of the grain boundary is about two three atoms. Most natural crystals are a atom by atom or molecule by molecule to complete but JillianBanfield and colleagues found some crystals, which are assembled from hundreds or thousands of atoms containing "prefabricated" nanocrystals made. According to the Review related article, block the growth pattern of such crystals might create artificial materials for optical and electronic devices (such as a laser or a hard disk) useful. Water stone (ferrihydrite) prefabricated natural crystals synthesized by bacteria in the mud flooded the mine can be found in the water by stone arranged nanocrystals grown connected. This way of introducing a unique crystal growth defects may affect the nature of the crystal in subsequent reactions. Two or more different kinds of crystals formed, non-parallel with the living body of law. Also known as the twins. Constitute twinning between two single crystal, the crystal surface will have a corresponding portion of the corresponding crystal edge parallel to each other, but not all one-day parallel Shandong Yue, however, they will be reflected by a rotation of 180 ° or reverse stretch (inversion) of symmetry operations to achieve coincide with each other or completely parallel. Double crystal element refers to characterize the imaginary geometric elements in symmetric double crystal orientation relationship between the orientation of the single crystal. It comprises: twin planes, for an imaginary plane. Reflected by its constitution allows two single crystal twinning coincide or completely parallel. Thus, the twin plane lattice must be both equal and parallel to a mutually consistent public face net. Symbolic form direction with parallel twin planes in a crystal plane or perpendicular to a zone axis to represent. Such as cassiterite geniculate double-crystal (Figure 1 cassiterite geniculate twinning), twin plane ‖ (101); orthoclase of Carlsbad twinning law (Figure 2 orthoclase of Carlsbad twin law Crystal), twin plane ⊥ (001). Twin plane can never be parallel to the single crystal of the symmetry plane, otherwise the two single crystals in a completely parallel to constitute a parallel relationship with students. Twin crystal axis of silicon carbide, an imaginary straight line. When it is rotated by 180 ° around. Crystal Materials Co., Ltd. Shandong days Yue, can constitute a single crystal twinning of two coincident or parallel to achieve complete agreement. Therefore, two crystal axes must be a reciprocal lattice both equal and parallel to the same public ranks. Twin crystal axis direction with a particular zone axis parallel or perpendicular to the crystal plane of a particular form of symbols represented. For example Carlsbad twinning law ‖ twin crystal axis (001); geniculate twin crystal twinning axis ⊥ (101). Double crystal axis must not parallel to the single crystal of the even symmetry axis. Twinning center for an imaginary point. Through its anti-stretch after Yue Crystal Materials Co., Ltd. Shandong days, can constitute two double crystal monomer coincident or parallel to achieve the same orientation (Figure 3 tetrahedrite twinning (circles represent double crystal center)). Bimorph center possible only appear in a single crystal itself has no center of symmetry of the case; and in general, it is just a derivative of the double-crystal elements, it can not be considered. Shandong days Yue crystal materials, new materials (certified), Jinan, Shandong days Yue provided by Spark Technology Development Company Limited. Jinan Spark Technology Development Co., Ltd. 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