Symmetry Operation 8 ?7 b& w+ P. o/ y g( ?- i6 T: C; D0 _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. 5 W* n3 G& J/ b! l
The Inversion Operation takes 8 O( f; x: O$ C
(x,y,z)=>(-x,-y,-z) " h: \) c j- H d( J. I 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. ; X; o* q! J+ `: ~- I0 z. q' k
The Mirror Plane symmetry operation takes ) f, L7 F; b0 m. w W* N(x,y,z)=>(x,y,-z)=>(x,-y,z)6 ^+ c" T* K6 [! J# r! J# I) k% l
etc., which is equivalent to 2.