Researchers devise an even harder diamond
(Kitco News) - Researchers believe they can improve on a diamond’s structure making an even harder material that could be useful for drilling and other tasks.
Dubbed the “pentadiamond” by its inventors, scientists at the University of Tsukuba came up with the diamond using computer calculations to devise the material.
The hardness comes from finding an ideal mix of chemical bonds.
"Diamonds, which are made entirely of carbon atoms arranged in a dense lattice, are famous for their unmatched hardness among known materials," said a news release explaining the findings. "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."
The University of Tsukuba investigated what would happen if carbon atoms were arranged in a more complex structure with a mixture of sp3 and sp2 hybridization.
"To calculate the most stable atomic configuration, as well as estimate its hardness, the team relied on a computational method called density functional theory (DFT). DFT has been successfully used throughout chemistry and solid-state physics to predict the structure and properties of materials. Keeping track of the quantum states of all of the electrons in a sample, and especially their interactions, is usually an intractable task. Instead, DFT uses an approximation that focuses on the final density of electrons in space orbiting the atoms."
Researchers said that the Young's modulus, a measure of hardness, of a pentadiamond was predicted to be almost 1700 GPa, compared with about 1200 GPa for a conventional diamond.