Atomic Testing Site Hosts Oldest Known Quasicrystals
Source image by Luca Bindi and Paul J. Steinhardt; composite by Abigail Malate.
(Inside Science) – Quasicrystals are mysterious structures whose existence was long thought to be impossible. They possess atoms arranged in orderly patterns that, unlike the atoms of regular crystals, never repeat themselves. Now scientists have found that the oldest known artificial quasicrystal may have unexpected origins -- the first atomic bomb test.
Quasicrystals are often thought of as delicate states of matter "that can only be formed if conditions are just so," said study senior author Paul Steinhardt, a theoretical physicist at Princeton University in New Jersey. But scientists are finding more evidence of quasicrystals forming during powerful shock waves, such as those from extraterrestrial impacts or supersonic projectiles fired at metal plates.
"This naturally led to the question: Could there be quasicrystals lurking in remnants of other shock phenomena, such as an atomic blast?" said study lead author Luca Bindi, a geologist, mineralogist and crystallographer at the University of Florence in Italy.
The scientists analyzed remnants from the first detonation of a nuclear bomb, the Trinity test at the Alamogordo Bombing Range in New Mexico in 1945. The resulting fireball fused the surrounding sand into a glassy material known as "trinitite." Although most trinitite is green, the researchers focused on red trinitite, which is rich in metals from the 30-meter tower supporting the bomb and the surrounding miles of copper wires that connected to recording equipment.
In a metallic blob just 10 microns across -- roughly a tenth the width of an average human hair -- the scientists discovered that the explosion synthesized a previously unknown quasicrystal made of silicon, copper, calcium and iron. Its pattern of fivefold, threefold and twofold symmetries are those expected of 20-sided, soccer-ball-shaped icosahedrons, unlike any seen in regular crystals.
This discovery "adds significant new support to the idea that high-pressure shocks, whether occurring in space in the early solar system, in a lab by firing projectiles at a target, or in an atomic blast, can lead to new forms of matter that were not known before -- in this case, new forms of quasicrystals," Bindi said.
Researchers may want to explore other extreme events, such as lightning strikes, in search of new forms of quasicrystals or even new forms of matter not yet conceived, Bindi added. "Who knows? Maybe quasicrystalline materials could be much more common than thought and simply missed so far."
The scientists detailed their findings online May 17 in the journal Proceedings of the National Academy of Sciences.