Chinese scientists have achieved a long-sought milestone in materials science by creating pure samples of hexagonal diamond, a rare carbon structure believed to surpass the hardness of natural diamond. Known as lonsdaleite, this material was first theorized in 1962 and later identified in meteorite fragments, but until now it had only been observed in tiny, impure forms that made its true properties difficult to verify, tells Live Science.
Unlike conventional diamond, which has a cubic crystal lattice, hexagonal diamond features a layered, honeycomb-like structure. This difference in atomic arrangement leads to stronger bonding between layers, which researchers have long predicted would make the material significantly harder and more durable than standard diamond.
To produce the material, the research team subjected highly ordered graphite to extreme conditions resembling meteorite impacts. Using pressures around 20 gigapascals and temperatures between 1,300°C and 1,900°C for extended periods, they successfully transformed the graphite into millimeter-scale samples of hexagonal diamond. These samples were large and pure enough for detailed structural and spectroscopic analysis, allowing scientists to confirm that the material is stiffer, harder, and more resistant to oxidation than cubic diamond.
The breakthrough resolves decades of debate over whether lonsdaleite exists as a distinct material or merely as a defect within regular diamond structures. By producing high-quality samples, researchers have established it as a separate and measurable form of carbon with superior mechanical properties.
Beyond its scientific significance, the development carries strong practical implications. A hexagonal diamond could enhance cutting tools, improve thermal management systems, and enable new applications in quantum sensing. Its formation process also offers insights into planetary science, particularly the conditions present during meteorite impacts and the evolution of carbon materials in extreme environments.
While large-scale production remains a challenge, the ability to synthesize and validate this elusive material marks a turning point. It expands the frontier of superhard materials and sets the stage for future advances in both industrial engineering and fundamental physics.