Nobel news

The 2011 Nobel prize for chemistry was awarded to Daniel Shechtman for the shocking discovery of quasicrystals, materials that are crystalline but break the symmetry rules and contain no repeating units.

Crystalline patterns

Until recently, textbooks would tell us that the arrangement of atoms in solids have short-range and long-range order. Chemical bonds between atoms give rise to the short-range order, even in so-called amorphous materials such as glass where local order exists. Crystalline materials have long-range order, recognised since Abbé Haüy in 1784, who explained how repeating units give rise to crystal shapes. Crystallography has shown repeatedly how crystals fit this pattern and how pentagonal symmetry could not exist. Pentagons, unlike triangles, squares and hexagons cannot tessellate, they cannot be laid together to form regular, repeating, 'crystalline' patterns, without gaps that break the symmetry and lead to long-range disorder in the pattern.