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A filled lens shape marking a twofold axis.
Also known as: Diad axis symbol, Two-fold axis mark, Lens symbol crystallography
The graphical symbol for a twofold rotation axis on a crystallographic space group diagram, drawn as a pointed oval.
Marks a twofold rotation axis, an axis about which the structure repeats after a half turn.
Contexts: Laboratory
Opens a graded family in which the number of points on the drawn figure equals the order of the axis, so the symbol can be counted rather than looked up.
Contexts: Laboratory
A small solid shape like a pointed oval or lens, its two ends coming to points on a single axis.