Named for their six-sided crystal structure, hexagonal diamonds are elusive : Hexagonal diamonds have been found at some meteorite impact sites, and others have been made briefly in labs.
Hex diamonds, however, have always been small or short-lived, so their rigidity has been difficult to measure. Now a larger hexagonal diamond has been conceived and we have the first proofs of its rigidity compared to the natural cubic diamond used, for example, in jewelery.
Stiffness is the ability of a material to resist deformation under force or pressure; For example, a rock is stiffer than rubber, since rubber bends when pressed. Hardness is resistance to scratching or other surface deformation .
As published in Physical Review B. , scientists from the Institute for Shock Physics at Washington State University created hexagonal diamonds large enough to measure their stiffness using sound waves .
For the study, they used gunpowder and compressed gas to propel small graphite discs the size of a dime at a speed of around 22,000 kilometers per hour over a transparent material. The impact produced shock waves in the discs that very quickly transformed them into hexagonal diamonds. Immediately after impact, the researchers produced a small sound wave and used lasers to measure its movement through the diamond.
As explained by Yogendra Gupta , director of the Institute of Shock Physics and corresponding author of the study:
Not only is it the strongest, it has beautiful optical properties and very high thermal conductivity. We have now created the hexagonal shape of the diamond, produced by impact compression experiments, which is significantly stiffer and stronger than normal gem diamonds.