Why do nanotubes grow chiral?

Rice University theorists determine factors that give tubes their chiral angles

Many a great idea springs from talks over a cup of coffee. But it’s rare and wonderful when a revelation comes from the cup itself.

Rice University theoretical physicist Boris Yakobson, acting upon sudden inspiration at a meeting last year in Arlington, Va., obtained a couple of spare coffee cups from a server and a pair of scissors and proceeded to lay out – science fair-style – an idea that could have far-reaching implications for the nanotechnology industry.

As reflected in a new paper in Nature Communications, Yakobson and his Rice colleagues, postdoctoral researcher Vasilii Artyukhov and research scientist Evgeni Penev, had come up with the seed (or perhaps, bean) of a simple formula that describes why nanotubes have chirality. Chirality is the property that describes the angle of the carbon atom hexagons that make up a nanotube’s walls.

– See more at: Rice News

Phosphorus a promising semiconductor

Rice University physicists find 2-D form pays no heed to defects

Defects damage the ideal properties of many two-dimensional materials, like carbon-based graphene. Phosphorus just shrugs.

That makes it a promising candidate for nano-electronic applications that require stable properties, according to new research by Rice University theoretical physicist Boris Yakobson and his colleagues.

In a paper in the American Chemical Society journal Nano Letters, the Rice team analyzed the properties of elemental bonds between semiconducting phosphorus atoms in 2-D sheets. Two-dimensional phosphorus is not theoretical; it was recently created through exfoliation from black phosphorus.

– See more at: Rice News

Carbyne morphs when stretched

Rice University calculations show carbon-atom chain would go metal to semiconductor

Applying just the right amount of tension to a chain of carbon atoms can turn it from a metallic conductor to an insulator, according to Rice University scientists.

Stretching the material known as carbyne — a hard-to-make, one-dimensional chain of carbon atoms — by just 3 percent can begin to change its properties in ways that engineers might find useful for mechanically activated nanoscale electronics and optics.

The finding by Rice theoretical physicist Boris Yakobson and his colleagues appears in the American Chemical Society journal Nano Letters.

– See more at: Rice News

Caps not the culprit in nanotube chirality

Rice study narrows the possibilities for gaining control of nanotube type

A single-walled carbon nanotube grows from the round cap down, so it’s logical to think the cap’s formation determines what follows. But according to researchers at Rice University, that’s not entirely so.

Theoretical physicist Boris Yakobson and his Rice colleagues found through exhaustive analysis that those who wish to control the chirality of nanotubes – the characteristic that determines their electrical properties – would be wise to look at other aspects of their growth.

In the study by Yakobson, research scientist Evgeni Penev and postdoctoral researcher Vasilli Artyukhov that was published recently by the American Chemical Society journal ACS Nano, the Rice researchers found that the elastic energy landscapes involved in cap formation are not strong enough to dictate the nanotube’s chirality….more

Flat boron by the numbers

Rice University researchers calculate what it would take to make new two-dimensional material

It would be a terrible thing if laboratories striving to grow graphene from carbon atoms kept winding up with big pesky diamonds.

“That would be trouble, cleaning out the diamonds so you could do some real work,” said Rice University theoretical physicist Boris Yakobson, chuckling at the absurd image.

Yet something like that keeps happening to experimentalists working to grow two-dimensional boron. Boron atoms have a strong preference to clump into three-dimensional shapes rather than assemble into pristine single-atom sheets, like carbon does when it becomes graphene. And boron clumps aren’t nearly as sparkly…more

Advanced Materials is Owl about Rice

High-impact journal publishes centennial edition with broad overview of materials science at Rice

Materials scientists who received Volume 24, Issue 36 of the respected journal Advanced Materials recently may have noticed it contained Rice University research and nothing else.

That is no mistake. The journal published a special issue this fall focused on Rice, the home of a large number of materials researchers that has been recognized by a Times Higher Education survey as the best in the world.  more…

Flat boron may take many forms

When is nothing really something? When it leads to a revelation about boron, an element with worlds of unexplored potential.

Theoretical physicist Boris Yakobson and his team at Rice University have taken an unusual approach to analyzing the possible configurations of two-dimensional sheets of boron, as reported this week in the American Chemical Society journal Nano Letters. more…

Rice professor’s nanotube theory confirmed

Air Force Research Laboratory experiment shows chirality of tube controls speed of growth

The Air Force Research Laboratory in Dayton, Ohio, has experimentally confirmed a theory by Rice University Professor Boris Yakobson that foretold a pair of interesting properties about nanotube growth: That the chirality of a nanotube controls the speed of its growth, and that armchair nanotubes should grow the fastest. more…

Graphene rips follow rules

A press release from Rice University Office of Public Affairs / News & Media Relations covers recent work by our group published in Nano Letters:

Rice University simulations show carbon sheets tear along energetically favorable lines

HOUSTON — (Jan. 5, 2012) — Research from Rice University and the University of California at Berkeley may give science and industry a new way to manipulate graphene, the wonder material expected to play a role in advanced electronic, mechanical and thermal applications.

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Recent book from a group member

Evgeni Penev from Yakobson’s group has co-authored a book on the theory of high-temperature superconductivity. The book is published by World Scientific  and includes 34 figures, more than 700 equations, and 543 references. The authors analyze those basic properties for which understanding can be achieved within the framework of traditional methods of theoretical physics.

IndustryWeek: “Nanotechnology: Beyond the Hype”

IndustryWeek has selected an image related to our very recent work on vacancy clusters in graphane as quantum dots as a front cover for its November 2010 issue.

In a recent article in ACS Nano, we discuss how complementary electronic properties and a tendency to form sharp graphenegraphane interfaces can open tantalizing possibilities for two-dimensional nanoelectronics. First-principles density functional and tight-binding calculations show that graphane can serve as natural host for graphene quantum dots, clusters of vacancies in the hydrogen sublattice. Their size n, shape, and stability are governed by the aromaticity and interfaces, resulting in formation energies ~1/√n eV/atom and preference to hexagonal clusters congruent with lattice hexagons. Clusters exhibit large gaps ~15/√n eV with size dependence typical for confined Dirac fermions.

Rice physicists dig theoretical wells to mine quantum dots

Graphane is the material of choice for physicists on the cutting edge of materials science, and Rice University researchers are right there with the pack – and perhaps a little ahead.

Researchers mentored by Boris Yakobson, a Rice professor of mechanical engineering and materials science and of chemistry, have discovered the strategic extraction of hydrogen atoms from a two-dimensional sheet of graphane naturally opens up spaces of pure graphene that look – and act – like quantum dots.