Supercarbon: “Denser than diamond”

Compiled by Photonics Spectra staff

Three newly discovered carbon structures may be at least three percent denser, more brilliant and better able to handle pressure than diamond can. Newly discovered modifications of carbon, such as graphene, have resulted in a scientific and technological revolution. The same could happen now, if scientists can synthesize these new carbon forms.

Scientists at Stony Brook University and the University of Oviedo in Spain have predicted three new carbon forms.

With a unique range of structures and properties – from ultrasoft graphite to superhard diamond – elemental carbon also includes symmetric fullerenes, carbon nanotubes, elusive carbines and M-carbon.

Graphene is the densest two-dimensional material, offering unique mechanical and electronic properties. It has some electrons that move with near-light velocities and that behave as if they had zero mass. The hardest known material, diamond has set several records. It has denser packing of atoms than any other known 3-D material and, when doped by boron, displays superconductivity and is the only known material that simultaneously displays superconductivity and superhardness.

Now, the researchers are proposing that the new carbon structures should be more than three percent denser than diamond, meaning that their electrons should have a higher kinetic energy and move more quickly. Their calculations show that the new modifications are almost as hard as diamond, but do not exceed it. In addition, they have diverse electronic properties, with bandgaps from 3 to 7.3 eV. Such a range implies the possibility of tuning the electronic properties.

The carbon also features ultralow compressibility. When subjected to pressure, it contracts less than most materials, even slightly less than diamond. In addition, the new carbons have higher refractive indices and stronger light dispersion than diamond.

If synthesized, these carbons could play an important technological role.

Findings were reported in the May 26 issue of Physical Review B (doi: 10.1103/PhysRevB.83.193410).