Calculations show carbyne chains will be twice the tensile strength of graphene three times the stiffness of diamond

Carbyne will be the strongest of a new class of microscopic materials if and when anyone can make it in bulk.

If they do, they’ll find carbyne nanorods or nanoropes have a host of remarkable and useful properties, as described in a new paper by Rice University theoretical physicist Boris Yakobson and his group.

Carbyne is a chain of carbon atoms held together by either double or alternating single and triple atomic bonds. That makes it a true one-dimensional material, unlike atom-thin sheets of graphene that have a top and a bottom or hollow nanotubes that have an inside and outside.

According to the portrait drawn from calculations by Yakobson and his group:

* Carbyne’s tensile strength – the ability to withstand stretching – surpasses “that of any other known material” and is double that of graphene. (Scientists had already calculated it would take an elephant on a pencil to break through a sheet of graphene.)

* It has twice the tensile stiffness of graphene and carbon nanotubes and nearly three times that of diamond.

* Stretching carbyne as little as 10 percent alters its electronic band gap significantly.

* If outfitted with molecular handles at the ends, it can also be twisted to alter its band gap. With a 90-degree end-to-end rotation, it becomes a magnetic semiconductor.

* Carbyne chains can take on side molecules that may make the chains suitable for energy storage.

* The material is stable at room temperature, largely resisting crosslinks with nearby chains.

ACS Nano – Carbyne from First Principles: Chain of C Atoms, a Nanorod or a Nanorope

Arxiv – Carbyne from First Principles: Chain of C Atoms, a Nanorod or a Nanorope

“You could look at it as an ultimately thin graphene ribbon, reduced to just one atom, or an ultimately thin nanotube,” he said. It could be useful for nanomechanical systems, in spintronic devices, as sensors, as strong and light materials for mechanical applications or for energy storage.

“Regardless of the applications,” he said, “academically, it’s very exciting to know the strongest possible assembly of atoms.

ABSTRACT

We report an extensive study of the properties of carbyne using first-principles calculations. We investigate carbyne’s mechanical response to tension, bending, and torsion deformations. Under tension, carbyne is about twice as stiff as the stiffest known materials and has an unrivaled specific strength of up to 7.5×107 N∙m/kg, requiring a force of ~10 nN to break a single atomic chain. Carbyne has a fairly large room-temperature persistence length of about 14 nm. Surprisingly, the torsional stiffness of carbyne can be zero but can be ‘switched on’ by appropriate functional groups at the ends. We reconstruct the equivalent continuum-elasticity representation, providing the full set of elastic moduli for carbyne, showing its extreme mechanical performance (e.g. a Young’s modulus of 32.7 TPa with an effective mechanical thickness of 0.772 Å). We also find an interesting coupling between strain and band gap of carbyne, which is strongly increased under tension, from 3.2 to 4.4 eV under a 10% strain. Finally, we study the performance of carbyne as a nanoscale electrical cable, and estimate its chemical stability against self-aggregation, finding an activation barrier of 0.6 eV for the carbyne–carbyne cross-linking reaction and an equilibrium cross-link density for two parallel carbyne chains of 1 cross-link per 17 C atoms (2.2 nm).

SOURCES – ACS Nano, Arxiv, Rice University

If you liked this article, please give it a quick review on ycombinator or StumbleUpon. Thanks

Subscribe on Google News