Dan Shechtman saw a symmetry the definition of a crystal did not allow
On April 8, 1982, Dan Shechtman observed fivefold symmetry in an aluminium and manganese alloy that did not fit the accepted definition of a crystal. Colleagues doubted and sometimes mocked the finding. He continued his research and won the Nobel Prize in Chemistry about thirty years later for discovering quasicrystals.
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Research, hypotheses and ideas at the boundaries of knowledge.
Three question marks in a notebook
In 1982, Dan Shechtman examined a rapidly cooled alloy and saw an electron diffraction pattern with tenfold symmetry. He marked three question marks in his notebook: the pattern did not fit the periodic lattice underlying the accepted crystal definition.
Why experts called it impossible
The crystal definition then relied on a periodic lattice. Twofold, threefold, fourfold and sixfold rotational symmetry fit such a lattice; fivefold and tenfold did not. Researchers therefore examined whether overlapping crystals or twinning produced the pattern. Resolving that question required more samples and measurements.
Pauling was not persuaded
Linus Pauling, the winner of two Nobel Prizes and one of the twentieth century's most influential chemists, argued that the patterns came from complex periodic crystals and twinning. He is widely remembered for saying there were no quasicrystals, only quasi scientists. The insult became the emblem of the dispute, but the question was not settled by wit. More samples, improved diffraction and a theory of quasiperiodic order accumulated until the alternative explanation lost force.
The paper that changed the definition
In November 1984, Shechtman, Ilan Blech, Denis Gratias and John Cahn published Metallic Phase with Long Range Orientational Order and No Translational Symmetry. It described long range orientational order without the periodic translation then considered essential. The International Union of Crystallography eventually broadened the definition: a crystal is a solid with an essentially discrete diffraction diagram, not necessarily a repeating lattice.
What the video contributes
In his Nobel lecture and official interviews, Shechtman describes the discovery and opposition to his interpretation. His account documents the dispute; the original paper presents what the diffraction pattern showed.
What this story does not prove
Acceptance rested on samples, measurements and work by additional researchers. The 1984 paper by Shechtman and colleagues presents the order observed in the material and the translational periodicity that was absent.
The pattern in the 1984 paper
The linked 1984 paper contains the diffraction evidence behind the revised understanding of crystal order. Its figures are the next step from Shechtman's account to the measured structure.
Sources and context
Shechtman and his colleagues published the original paper in Physical Review Letters in November 1984. The Nobel Committee awarded him the 2011 chemistry prize for the discovery of quasicrystals, ordered structures that are not periodic.
Popular accounts compress years of scientific dispute into a personal duel with Linus Pauling. Sources confirm that Pauling rejected the quasicrystal interpretation, but the field changed through replication, calculation and work by many other researchers as well.