Researchers discover why atoms in solids show a preference for certain structures
The process involved here sounds unwieldy, but is, in fact, quite simple: a material has a 6-fold rotation symmetry if the arrangement of its atoms remains unchanged when it is rotated by 60 degrees - one sixth of a circle. The atoms in metals often order themselves in this way. However, more complicated structures with 5-fold, 8-fold or 10-fold rotation symmetry also exist. 'It is surprising that materials with 7-fold, 9-fold or 11-fold symmetry have not yet been observed in nature,' says Clemens Bechinger, fellow at the Max Planck Institute for Metals Research and Professor at the University of Stuttgart: 'This is all the more astonishing in view of the fact that patterns with any rotation symmetry can be drawn without difficulty on paper.' The question is, therefore, whether such materials have simply been overlooked up to now or whether nature has an aversion to certain symmetries...