More than 80 years after the atomic bombing of the Japanese city of Hiroshima, researchers have found, inside a microscopic grain of blast debris, a metal alloy with an atomic structure never before recorded in nature or in materials manufactured in laboratories.
The discovery came during a study of what is known as "Hiroshimaite," which are tiny glass droplets that formed when the enormous heat from the explosion melted the city's buildings, soil, metals, and glass, then ejected the molten and vaporized material into the air, where it cooled rapidly and later fell into the Hiroshima Bay area.
The study was published in the journal Science Advances and was conducted by an international team led by mineralogist and crystallographer Luca Bindi from the University of Florence, Italy.
The researchers explained that the discovery provides a rare example of how extremely violent conditions can produce materials that do not form in normal natural or industrial environments.
The team examined 34 pieces of Hiroshimaite granules, ranging in size from a few hundred micrometers to several millimeters. Using electron microscopes to analyze their composition, the researchers found several tiny metal crystals within one of the glass granules.
Scientists extracted four mineral grains, each measuring only about 10 micrometers in size—much smaller than the width of a human hair. Analysis showed that most were composed of relatively common alloys rich in iron and chromium, but one grain was entirely different.
The exceptional crystal contained a homogeneous mixture of iron, chromium, nickel, manganese, molybdenum, and aluminum, along with a high percentage of silicon. The novelty lay not in the presence of these elements—they are all well-known—but in the unprecedented way their atoms were arranged within the crystal.
Using X-ray diffraction, the researchers found that the alloy has a cubic and ordered crystal structure, and scientists have never before documented this combination of elements within this specific atomic structure.
How did the explosion create the alloy?
On August 6, 1945, an atomic bomb exploded over Hiroshima, creating a fireball with temperatures reaching thousands of degrees Celsius. The intense heat and pressure vaporized a complex mixture of steel, aluminum alloys, glass, concrete, soil, and other materials within the city.
As the fireball expanded and cooled rapidly, the metallic vapors began to condense and form tiny droplets. However, the cooling process occurred too quickly, so the atoms did not have enough time to transition into the more stable arrangements that typically form when metals cool slowly.
As a result, some atoms froze into unfamiliar positions, forming alloys and crystals that are difficult to produce under conventional conditions.
The team suggests that the new alloy was formed from mixed metallic vapor, and its composition was then preserved due to what is known as ultrafast cooling inside the expanding fireball.
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