Diamond will always be a girl's best friend, but it may soon lose favour with industrial drillers.
The gemstone lost its title of the "world's hardest material" to
Zicheng Pan at Shanghai Jiao Tong University and colleagues simulated how atoms in two substances believed to have promise as very hard materials would respond to the stress of a finely tipped probe pushing down on them.
The first, wurtzite boron nitride has a similar structure to diamond, but is made up of different atoms.
The second, the mineral lonsdaleite, or hexagonal diamond is made from carbon atoms just like diamond, but they are arranged in a different shape.
Only small amounts of wurtzite boron nitride and lonsdaleite exist naturally or have been made in the lab so until now no one had realised their superior strength. The simulation showed that wurtzide boron nitride would withstand 18% more stress than diamond, and lonsdaleite 58% more. If the results are confirmed with physical experiments, both materials would be far harder than any substance ever measured.
Doing those tests won't be easy, though. Because both are rare in nature, a way is needed to make enough of either of them to test the prediction.
Rare mineral lonsdaleite is sometimes formed when meteorites containing graphite hit Earth, while wurtzite boron nitride is formed during volcanic eruptions that produce very high temperatures and pressures.
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