For more than two centuries, the fundamental axiom of crystallography held that any ordered solid had to possess a periodic structure that repeated infinitely in space, admitting only 2, 3, 4, or 6-fold rotational symmetries. However, in April 1982, physicist Dan Shechtman observed under his electron microscope an aluminum-manganese alloy with a 10-fold symmetry diffraction pattern: something formally classified as a mathematical absurdity.
The initial rejection from the scientific community was relentless. The head of his laboratory asked him to leave the team for bringing disrepute to the center, and two-time Nobel laureate Linus Pauling went so far as to publicly ridicule him, stating that "there are no quasicrystals, only quasi-scientists." Nevertheless, Shechtman was right: he had discovered quasicrystals, a form of non-periodic atomic order similar to Roger Penrose's geometric tilings, where atoms follow an ordered pattern that never repeats itself exactly.
These materials possess unusual characteristics:
- Anomalous properties: Although they are metallic alloys, they are terrible conductors of heat and electricity, extremely hard, and remarkably slippery.
- Extraterrestrial origin: Although for decades they were believed to be exclusive to the laboratory, in 2009 natural quasicrystals were discovered in fragments of the Khatyrka meteorite, formed in extreme cosmic collisions 4,500 million years ago.
The discovery, which earned Shechtman the Nobel Prize in Chemistry in 2011, forced the International Union of Crystallography to redefine the very concept of what we consider a crystal.
Source: The Nobel Prize in Chemistry 2011 - Dan Shechtman / Nature Materials
