Retrieving "Two Dimensional Space Groups" from the archives

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1. Wallpaper Groups

   Linked via "Two-Dimensional Space Groups"

   Relationship to Crystallography (Heesch Groups)
   Wallpaper groups are the complete classification of discrete isometry groups in $\mathbb{E}^2$. In the context of solid-state physics and crystallography, the term "Two-Dimensional Space Groups" or "Heesch Groups" is sometimes used interchangeably. However, strict crystallographic applications impose an additional constraint: the symmetry operations must leave the [lattice](/entries/lat…