Design and Properties of "Pentadiamond" Predicted Using Computers

takyon writes:

Building a Harder Diamond (SD)

Researchers at the University of Tsukuba used computer calculations to design a new carbon-based material even harder than diamond. This structure, dubbed "pentadiamond" by its creators, may be useful for replacing current synthetic diamonds in difficult cutting manufacturing tasks.

Diamonds, which are made entirely of carbon atoms arranged in a dense lattice, are famous for their unmatched hardness among known materials. However, carbon can form many other stable configurations, called allotropes. These include the familiar graphite in pencil lead, as well as nanomaterials such as carbon nanotubes. The mechanical properties, including hardness, of an allotrope depend mostly on the way its atoms bond with each other. In conventional diamonds, each carbon atom forms a covalent bond with four neighbors. Chemists call carbon atoms like this as having sp³ hybridization. In nanotubes and some other materials, each carbon forms three bonds, called sp² hybridization.

Now, researchers at the University of Tsukuba have explored what would happen if carbon atoms were arranged in a more complex structure with a mixture of sp³ and sp² hybridization.

[...] The scientists found that the Young's modulus, a measure of hardness, of pentadiamond was predicted to be almost 1700 GPa, compared with about 1200 GPa for conventional diamond.

Journal Reference:
Yasumaru Fujii, Mina Maruyama, Nguyen Thanh Cuong, Susumu Okada.Pentadiamond: A Hard Carbon Allotrope of a Pentagonal Network of sp² and sp³ C Atoms (DOI: 10.1103/PhysRevLett.125.016001) (DX)

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