Two-dimensional space groups with sevenfold symmetry
Acta Crystallographica Section A: Foundations of Crystallography
, Volume 42 (1): 55 – Jan 1, 1986
Abstract
Fivefold and sevenfold symmetry operations are, of course, incompatible with repetition by a lattice but, with the appearance of structures involving curved sheets, they and other non-crystallographic operations must now be taken into consideration as possibilities of non-Euclidean crystallography develop. Here are described the symmetry groups which might be called 732 and 73m and which may be found in two-dimensional manifolds.
