回反軸

rotary-inversion axis

[目次：結晶等(結晶構造／材料試料)]

結晶点群の対称要素の一つ。ある直線を軸として、結晶全体を一定角度(90°)、回転させた後に反転操作が行なわれたとき、操作前の結晶と一致する場合、この軸を回反軸という。

A symmetry element of the crystallographic point group. When the whole crystal (constituent atoms) is rotated by an angle of 90° with respect to a line, and successively an inversion is operated for the rotated crystal, the resultant crystal can be equivalent to the crystal before the operations. In this case, the combination of the two symmetries is called "rotary-inversion axis." Only the 4-fold rotary-inversion axis is a symmetry of the crystallographic point group.

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