An animation depicting the 4₁ (left) and 4₃ (right) screw axis as described in crystallography. The 4₁ screw axis is a combination of a 90° counterclockwise rotation followed by a c/4 translation down the c-axis, whereas the 4₃ screw axis is a combination of a 90° counterclockwise rotation followed by a 3c/4 translation down the c-axis. These symmetry elements are depicted inside of a generic tetragonal unit cell.
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