Symmetry Operation & x e q J! H. T8 _
Symmetry operations include the Improper Rotation, Inversion Operation, Mirror Plane, and Rotation. Together, these operations create 32 crystal classes corresponding to the 32 Point Groups. : D$ X3 Q! ~, B. Q
The Inversion Operation takes 0 _! y( [. B4 S. i, T+ v. d9 _9 Q(x,y,z)=>(-x,-y,-z) . {4 J- p' Q" b: T and is denoted i. When used in conjunction with a Rotation, it becomes an Improper Rotation. An Improper Rotation by 360/n . For periodic crystals, the Crystallography Restriction allows only the Improper Rotations 1, 2, 3, 4, and 6. . H- ~4 |- k8 i2 Z
The Mirror Plane symmetry operation takes 4 V9 Z D+ M, U$ y3 _: S9 a(x,y,z)=>(x,y,-z)=>(x,-y,z)4 D Y8 I3 ]* K2 Y, s2 j
etc., which is equivalent to 2.
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发表于 2009-2-2 22:45
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