New carbon allotrope could have a variety of applications

Apr 22, 2011 by Lisa Zyga feature
New carbon allotrope could have a variety of applications
The structure of the new carbon allotrope, T-carbon, is shown from different directions. T-carbon is obtained by replacing each carbon atom in diamond with a carbon tetrahedron. Image credit: Sheng, et al. ©2011 American Physical Society.

(PhysOrg.com) -- Carbon comes in many different forms, and now scientists have predicted another new form, or allotrope, of carbon. The new form of carbon, which they call T-carbon, has very intriguing physical properties that suggest that it could have a wide variety of applications.

The scientists, Xian-Lei Sheng, Qing-Bo Yan, Fei Ye, Qing-Rong Zheng, and Gang Su, from the Graduate University of Chinese Academy of Sciences in Beijing, China, have published their study on the first-principles calculations of T-carbon in a recent issue of .

Allotropes are formed when the atoms in a substance that contains only one type of atom are arranged differently. Although many substances have multiple allotropes, carbon has the greatest number of known allotropes. The three best-known carbon allotropes are amorphous carbon (such as coal and ), graphite, and diamond. Since the 1980s, scientists have been synthesizing newer allotropes, including carbon nanotubes, graphene, and fullerenes, all of which have had a significant scientific and technological impact.

With more recent advances in synthetic tools, scientists have been investigating a wide variety of new – and sometimes elusive – carbon allotropes. In light of these investigations, Sheng, et al., write in their study that it appears that we might be entering the era of carbon allotropes.

Here, the scientists explained how to obtain a new carbon allotrope by substituting each carbon atom in diamond with a carbon tetrahedron (hence the name “T-carbon”). They were inspired by the substitution of each carbon atom in methane with a carbon tetrahedron, which forms tetrahedrane.

“[Our study] adds a possible new allotrope of carbon with amazing properties,” Su told PhysOrg.com. “T-carbon has bond angles different from graphite and diamond, but the interesting structure is still quite stable and has the same group symmetry as diamond, thereby widening people’s vision and knowledge on carbon bonding.”

Each unit cell of the T-carbon structure contains two tetrahedrons with eight carbon atoms. As the scientists’ calculations showed, T-carbon is thermodynamically stable at ambient pressure and is a semiconductor. T-carbon is one-third softer than diamond, which is the hardest known natural material. The new carbon allotrope also has a much lower density than diamond, making it “fluffy.”

The scientists also calculated that T-carbon has large interspaces between compared to other forms of carbon, which could make it potentially useful for hydrogen storage. In addition, the unique physical properties of this new carbon allotrope make it a promising material for photocatalysis, adsorption, and aerospace applications.

“We believe that, if obtained, T-carbon is so fluffy that it can be used to store hydrogen, lithium, and other small molecules for energy purposes,” Su said. “It can be used as photocatalysis for water-splitting to generate hydrogen, or as an adsorption material for environmental protection. As it has very low density but a high modulus and hardness, it is quite suitable for aerospace materials, sports materials like a tennis racket, golf club, etc., and cruiser skin, and so forth.”

The scientists also noted that T-carbon could have astronomical implications as a potential component of interstellar dust and carbon exoplanets.

“There is a long-standing puzzle in astronomy known as the ‘carbon crisis’ in interstellar dust,” Su said. “Observations by the Hubble telescope revealed that the carbon budget in dust is deep in the red, and there is not sufficient carbon in dust to account for the light distortions.”

In addition, the exoplanet WASP-12b has recently been found to have a large amount of carbon, making it the first carbon-rich exoplanet ever discovered. Since the structure of the carbon in WASP-12b is still unclear, T-carbon might also be one of possible candidates for this carbon planet.

To investigate T-carbon further, the researchers would like to synthesize the new allotrope in the lab, although they say that this would likely be very difficult.

“A synthesis of T-carbon in the lab poses a great challenge for materials scientists and chemists,” Su said. “We suggest the following ways: using the CVD technique under a negative pressure environment; detonation on diamond or graphite; crystallization of amorphous tetragonal ; or stretching cubic diamond under extremely large strength.”

Explore further: Team reveals molecular structure of water at gold electrodes

More information: Xian-Lei Sheng, et al. “T-Carbon: A Novel Carbon Allotrope.” Physical Review Letters 106, 155703 (2011). DOI: 10.1103/PhysRevLett.106.155703

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fmfbrestel
2 / 5 (4) Apr 22, 2011
OK, materials science guys, once you get large sheets of graphene figured out and meter length nanotubes, here is your next project. Nice to have the job security if you're a materials science researcher, but it would be nice to get one of these tackled before racing to the next big thing.
Eikka
4.3 / 5 (6) Apr 22, 2011
Advances in science often occur laterally, and trying to solve the harder problem sometimes gives you the answer to the easier one that you couldn't solve.

What you're suggesting is like saying that Jules Verne shouldn't hypothesize about going to the moon before the Wright brothers have made an airplane first.
quasi44
5 / 5 (1) Apr 22, 2011
I think a highly significant, and lucrative use for this configuration would be helium storage, considering the high rate of loss in nature and the predictions that it will become quite scarce in a decade or so.
lib
2 / 5 (4) Apr 22, 2011
Well, there is nothing wrong with predictions to be bold but it is embarrassing when results published in a PRL-level journal show the lack of basic understanding of the subject.

For a person working in the field the claim that a new form of carbon was found to be "thermodynamically stable at ambient pressure" may sound like "we just found a few unaccounted trillion dollars to balance the budget". Sure enough, their calculations show that T-carbon is actually unfavored by 1.2-1.3 eV/atom (!) compared to diamond/graphite. The athours' comment that this only "suggests" "that this structure might be less thermodynamical stable against those allotropes at zero pressure" is, mildly put, an understatement. The proposed structure is not only ridiculously high in energy but it is also not dense meaning that application of pressure will further destabilize it. Temperature effects typically change the relative stability by much less than 0.1 eV/atom.
lib
1 / 5 (2) Apr 22, 2011
(cont) How exactly do the authors think their bulk structure could be synthesized, let alone used for applications? This makes you wonder whether the referees read the paper at all.
eachus
5 / 5 (2) Apr 22, 2011
I quote from the article: "They were inspired by the substitution of each carbon atom in methane with a carbon tetrahedron, which forms tetrahedrane."

No, it doesn't. It doesn't even come close. Tetra-tert-butyltetrahedrane was synthesized in 1978 with a tetrahedral carbon atom arrangement at its core, but the four butyl groups completely surround it and stabilize it. Interestingly, two other "platonic solids" have been created: Dodecahedrane (C20H20) and cubane (C8H8). You can only make these compounds where each carbon atom has bonds to three other carbon atoms. Five is right out, and with four, octahedrane? there are no bonds left for the hydrogen.

Are the referees Loony Toons? Not really, this is the way science works. The authors, computational chemists, designed and named the compound. Now "real" chemists can try and make it, or more likely make some related compound that they think is easier, like the tetra-tert-butyltetrahedrane mentioned above.
neiorah
4 / 5 (1) Apr 25, 2011
Come on guys you can do something about inappropriate content however I continually see these stupid advertisements in a place where thoughtful discussions should be.

DO SOMETHING TO GET THIS POLLUTION OUT OF THIS PLACE
PPihkala
4 / 5 (1) Apr 30, 2011
DO SOMETHING TO GET THIS POLLUTION OUT OF THIS PLACE

Every time I see pollution that has nothing to do with commenting, I report it as abuse. What might be more effective in the long run would be harder, slower process of getting the writing rights to physorg.com. Or maybe system where abuse votes from sufficient individuals would 'ban' writers and/or their comments without needing physorg staff intervention.