Quasicrystal growth observed in the lab

First spotted in 1982 by Dan Shechtman, quasicrystals have a subtle long-range order that enables them to evince rotational symmetries never seen in conventional crystals. (See Physics Today, December 2011, page 17.) When a quasicrystal grows, it incorporates material in small bits. For decades, theorists have been working to understand how the local incorporation and long-range order can be compatible. Now a team led by the University of Tokyo’s Keiichi Edagawa has imaged the quasicrystalline alloy Al_70.8Ni_19.7Co_9.5 as it adds on new material. They found that the growth process includes episodes in which the quasicrystal’s 10-fold rotational symmetry threatened to become lost. But during those episodes, the quasicrystal became strained; the molecular rearrangements that relaxed the strain defused the threat. Edagawa and colleagues reached those conclusions from a geometric analysis of images such as the one here, obtained with high-resolution transmission electron...