Design World

  • Home
  • Technologies
    • 3D CAD
    • Electronics • electrical
    • Fastening & Joining
    • Factory automation
    • Linear Motion
    • Motion Control
    • Test & Measurement
    • Sensors
    • Fluid power
  • Learn
    • Ebooks / Tech Tips
    • Engineering Week
    • Future of Design Engineering
    • MC² Motion Control Classrooms
    • Podcasts
    • Videos
    • Webinars
  • LEAP AWARDS
  • Leadership
    • 2022 Voting
    • 2021 Winners
  • Design Guide Library
  • Resources
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Women in Engineering
  • Supplier Listings

Carbyne Morphs when Stretched

By Rice University | July 21, 2014

Share

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.

Until recently, carbyne has existed mostly in theory, though experimentalists have made some headway in creating small samples of the finicky material. The carbon chain would theoretically be the strongest material ever, if only someone could make it reliably.

The first-principle calculations by Yakobson and his co-authors, Rice postdoctoral researcher Vasilii Artyukhov and graduate student Mingjie Liu, show that stretching carbon chains activates the transition from conductor to insulator by widening the material’s band gap. Band gaps, which free electrons must overcome to complete a circuit, give materials the semiconducting properties that make modern electronics possible.

In their previous work on carbyne, the researchers believed they saw hints of the transition, but they had to dig deeper to find that stretching would effectively turn the material into a switch.

Each carbon atom has four electrons available to form covalent bonds. In their relaxed state, the atoms in a carbyne chain would be more or less evenly spaced, with two bonds between them. But the atoms are never static, due to natural quantum uncertainty, which Yakobson said keeps them from slipping into a less-stable Peierls distortion.

“Peierls said one-dimensional metals are unstable and must become semiconductors or insulators,” Yakobson said. “But it’s not that simple, because there are two driving factors.”

One, the Peierls distortion, “wants to open the gap that makes it a semiconductor.” The other, called zero-point vibration (ZPV), “wants to maintain uniformity and the metal state.”

Yakobson explained that ZPV is a manifestation of quantum uncertainty, which says atoms are always in motion. “It’s more a blur than a vibration,” he said. “We can say carbyne represents the uncertainty principle in action, because when it’s relaxed, the bonds are constantly confused between 2-2 and 1-3, to the point where they average out and the chain remains metallic.”

But stretching the chain shifts the balance toward alternating long and short (1-3) bonds. That progressively opens a band gap beginning at about 3 percent tension, according to the computations. The Rice team created a phase diagram to illustrate the relationship of the band gap to strain and temperature.

How carbyne is attached to electrodes also matters, Artyukhov said. “Different bond connectivity patterns can affect the metallic/dielectric state balance and shift the transition point, potentially to where it may not be accessible anymore,” he said. “So one has to be extremely careful about making the contacts.”

“Carbyne’s structure is a conundrum,” he said. “Until this paper, everybody was convinced it was single-triple, with a long bond then a short bond, caused by Peierls instability.” He said the realization that quantum vibrations may quench Peierls, together with the team’s earlier finding that tension can increase the band gap and make carbyne more insulating, prompted the new study.

“Other researchers considered the role of ZPV in Peierls-active systems, even carbyne itself, before we did,” Artyukhov said. “However, in all previous studies only two possible answers were being considered: either ‘carbyne is semiconducting’ or ‘carbyne is metallic,’ and the conclusion, whichever one, was viewed as sort of a timeless mathematical truth, a static ‘ultimate verdict.’ What we realized here is that you can use tension to dynamically go from one regime to the other, which makes it useful on a completely different level.”

Yakobson noted the findings should encourage more research into the formation of stable carbyne chains and may apply equally to other one-dimensional chains subject to Peierls distortions, including conducting polymers and charge/spin density-wave materials.

The Robert Welch Foundation, the U.S. Air Force Office of Scientific Research and the Office of Naval Research Multidisciplinary University Research Initiative supported the research. The researchers utilized the Data Analysis and Visualization Cyberinfrastructure (DAVinCI) supercomputer supported by the NSF and administered by Rice’s Ken Kennedy Institute for Information Technology.


Filed Under: Materials • advanced

 

Related Articles Read More >

Self-lubricating and wear-resistant: igus bar stock for food, continuous operation and high media resistance
Minnesota Rubber and Plastics announces plans for new Innovation Center
The importance of resin selection
EXE014 - Image 1
Composite materials help place Italian race team in pole position

DESIGN GUIDE LIBRARY

“motion

Enews Sign Up

Motion Control Classroom

Design World Digital Edition

cover

Browse the most current issue of Design World and back issues in an easy to use high quality format. Clip, share and download with the leading design engineering magazine today.

EDABoard the Forum for Electronics

Top global problem solving EE forum covering Microcontrollers, DSP, Networking, Analog and Digital Design, RF, Power Electronics, PCB Routing and much more

EDABoard: Forum for electronics

Sponsored Content

  • Renishaw next-generation FORTiS™ enclosed linear encoders offer enhanced metrology and reliability for machine tools
  • WAGO’s smartDESIGNER Online Provides Seamless Progression for Projects
  • Epoxy Certified for UL 1203 Standard
  • The Importance of Industrial Cable Resistance to Chemicals and Oils
  • Optimize, streamline and increase production capacity with pallet-handling conveyor systems
  • Global supply needs drive increased manufacturing footprint development

Design World Podcasts

June 12, 2022
How to avoid over engineering a part
See More >
Engineering Exchange

The Engineering Exchange is a global educational networking community for engineers.

Connect, share, and learn today »

Design World
  • Advertising
  • About us
  • Contact
  • Manage your Design World Subscription
  • Subscribe
  • Design World Digital Network
  • Engineering White Papers
  • LEAP AWARDS

Copyright © 2022 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy | Advertising | About Us

Search Design World

  • Home
  • Technologies
    • 3D CAD
    • Electronics • electrical
    • Fastening & Joining
    • Factory automation
    • Linear Motion
    • Motion Control
    • Test & Measurement
    • Sensors
    • Fluid power
  • Learn
    • Ebooks / Tech Tips
    • Engineering Week
    • Future of Design Engineering
    • MC² Motion Control Classrooms
    • Podcasts
    • Videos
    • Webinars
  • LEAP AWARDS
  • Leadership
    • 2022 Voting
    • 2021 Winners
  • Design Guide Library
  • Resources
    • 3D Cad Models
      • PARTsolutions
      • TraceParts
    • Digital Issues
      • Design World
      • EE World
    • Women in Engineering
  • Supplier Listings