Scientists found the oldest synthetic quasicrystal in the wreckage of the first atomic bomb test almost 76 years ago.
The report brings together two of the strangest phenomena in chemistry. On July 16, 1945, the Trinity test was the first nuclear detonation carried out in the New Mexico desert as part of the Manhattan Project during World War II. In the resulting explosion, particles of silica-based desert sand were sucked into the fireball from the explosion before raining down as a vitreous mineral called trinitite. These fragments are usually green, but red trinitite is also occasionally found, formed where the sand has fused with copper oxide from the test recorder. The exact conditions that led to the formation of Trinitite are still unknown and it remains a crime to remove the stones from the desert.
A group led by geologist Luca Bindi from the University of Florence (Italy) and the theoretical physicist Paul Steinhardt from Princeton University (USA) has now reported on a new icosahedral quasicrystal, Si61Cu30thApprox.7thFe2found in a 1 cm long sample of red trinitite. Quasicrystals are another scientific puzzle. Their atomic structure is ordered, but their pattern is not repeated as in normal crystals. This was considered impossible until it was discovered by Dan Schechtman with the Nobel Prize in 1982, when Steinhardt suggested the name “quasicrystal”.
Knowing that high temperature and high pressure environments can create quasicrystals, the team decided to investigate nuclear explosion debris from the Trinity test. Since most quasicrystals are metal alloys, group 12 isolated “metal blobs” from their sample and examined them using X-ray diffraction. This resulted in a metal droplet that contained a structure with five, three and two axes of symmetry – a combination that can only exist in a quasicrystal.
The trinitite sample is probably the first quasicrystal human ever to be synthesized, albeit without knowing it. Before the Trinity test, scientists were unable to create the extreme environments required for such a material to form. The work ties in with Bindis and Steinhardt’s discovery of the first naturally occurring quasicrystal, icosahedrite (Al62Cu24Fe13th), found in the Khatyrka meteorite in 2010, which may date back to the origins of the solar system.
Chloe Bonamici, an assistant professor at the University of Wisconsin-Madison who specializes in isotope geochemistry, says the work supports the idea that “in a nuclear fireball is a very unusual bonding environment.” “The discovery could also support the idea of an important role for the condensation of vapors and plasmas in a nuclear fireball, as many man-made quasicrystals are made by vapor deposition and plasma spraying,” she adds.
The discovery means that other nuclear test sites could spawn new quasicrystals, which will help us understand how they can form in nature and give us a clearer picture of the complex forces at work within a nuclear explosion. “Right now,” says Bonamici, “the quasicrystal is a tiny, tantalizing secret in another, larger secret.”