Super carbon denser than diamonds

STONY BROOK U. (US) — Three newly discovered structures of carbon may be three percent denser, more brilliant, and better able to handle pressure than diamonds.

The research is reported in the journal Physical Review B.

Newly discovered modifications of carbon, such as graphene, have previously resulted in a scientific and technological revolution. The same could happen now, if scientists can find a way to synthesize these new forms of carbon.

Elemental carbon possesses a unique range of structures and properties—from ultrsoft graphite to superhard diamond, and also including elusive carbines, symmetric fullerenes, carbon nanotubes, and M-carbon.

Graphene is the densest two-dimensional material, with unique mechanical and electronic properties and having some electrons moving with near-light velocities and behaving as if they had zero mass.

Diamond has set several records—not only is it the hardest known material, but it also has denser packing of atoms than any other known three-dimensional material. When doped by boron, diamond displays superconductivity and is the only know materials simultaneously displaying superhardness and superconductivity.

Artem Oganov, professor of geosciences and physics at Stony Brook University and graduate student Qiang Zhu propose the new structures of carbon should be more than 3 percent denser than diamond, meaning their electrons should have a higher kinetic energy and move faster.

Zhu’s calculations show that the new modifications are almost as hard as diamond, but don’t exceed it and have diverse electronic properties are very diverse, with the band gap ranging from 3.0 eV to 7.3 eV.

Band gap is the amount of energy needed to close the circuit and is the most important characteristic of the electronic structure of materials. Such a wide range of band gaps implies the possibility of tuning the electronic properties.

The new carbons also have ultralow compressibility—when subjected to pressure, they will contract less than most materials (even slightly less than diamond, the current record holder).

They have higher refractive indices and stronger light dispersion than diamond—which means better brilliance and color effects than those displayed by diamond.

“Carbon is an inexhaustible element in its chemical diversity and in the multitude of its physical applications”, Oganov says.

“If these predicted forms of carbon can be synthesized, they may find important technological roles.”

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