Nanotechnology Now

Our NanoNews Digest Sponsors

Heifer International

Wikipedia Affiliate Button

Home > Press > Study resolves controversy about electron structure of defects in graphene

Abstract:
Researchers in Brazil calculated the overall electron structure of the vacancy region of a crystal lattice through the unprecedented use of a hybrid functional method, which yielded results compatible with experimental data.

Study resolves controversy about electron structure of defects in graphene

São Paulo', Brazil | Posted on December 21st, 2017

A study conducted at the University of São Paulo's Physics Institute (IF-USP), Brazil, has resolved a longstanding controversy dogging the international community of researchers dedicated to investigating defects in graphene. The controversy is related to the calculation of the overall electronic structure of defects. This configuration, which comprises many variables, was described in different ways depending on the researcher and the model used. The solution, which is identical for all models and compatible with experimental findings, was obtained by Chilean Ana María Valencia García and her PhD supervisor, Marília Junqueira Caldas, Full Professor at IF-USP.

An article authored by both researchers has been published in the journal Physical Review B with the title "Single vacancy defect in graphene: Insights into its magnetic properties from theoretical modeling". The journal's editors chose one of the figures from the article for inclusion in the Kaleidoscope section, which promotes interest in the esthetics of physics by featuring images selected for their artistic appeal.

García received a PhD scholarship from Chile's National Scientific & Technological Research Commission (CONICYT), while Caldas was supported by the National Organic Electronics Institute (INEO), which is funded jointly by FAPESP and Brazil's National Council for Scientific & Technological Development (CNPq).

"There were divergences in the community regarding whether the vacancy formed by removing a single carbon atom from a graphene sheet's crystal lattice causes a weak or strong magnetic moment, and regarding the strength of the magnetic interaction between vacancies," Caldas said. The vacancy prompts the surrounding atoms to rearrange themselves into new combinations to accommodate the absence of an atom, forming electron clusters known as "floating orbitals" at the vacant site.

Three important variables are associated with the phenomenon: electron density, i.e., how the electrons are distributed; electron levels, i.e., the energy levels occupied by the electrons; and magnetic moment, i.e., the torque produced in the electrons by an external magnetic field.

First-hand use of hybrid method in graphene

Reflecting on the divergence, Caldas finds strange that its proponents are all excellent researchers affiliated with renowned international institutions. Studies conducted by the research revealed that the divergent values derived from the use of different simulation methods.

"There are two ways to calculate the overall electron structure of the vacancy region, both derived from quantum mechanics: the Hartree-Fock (HF) method, and density functional theory (DFT). In DFT the calculation is performed by making each electron interact with average electron density, which includes the electron in question. In HF the operator used excludes the electron and considers only its interaction with the others. HF produces more precise results for electron structure but the calculation is far more laborious," Caldas said.

"The two methods are often combined by means of hybrid functionals, which have been mentioned in the scientific literature since the end of the twentieth century. I worked with them myself some time ago in a study on polymers, but they had never been used in the case of graphene. What Ana María [Valencia García] and I did was discover the hybrid functional that best describes the material. Applied to several models using computer simulation, our hybrid functional produced the same result for them all and this result matched the experimental data."

Besides resolving the controversy, which had lasted years, and having one of its images selected for esthetic value, another interesting aspect of this research is the problem that motivated it. "We came to it via the interest aroused by a material known as anthropogenic dark earth or ADE," Caldas explained. "ADE is a kind of very dark, fertile soil found in several parts of the world including the Amazon. It retains moisture even at high temperatures and remains fertile even under heavy rain. It's called anthropogenic because its composition derives from middens and cultivation by indigenous populations in the pre-Columbian period at least two millennia ago. This intriguing material was known to have resulted from multi-stacked layers of graphene nanoflakes. It was our interest in ADE that led us to study the phenomenon of vacancy in graphene sheets."

In conclusion, it should be noted that there are potential applications of vacancy in graphene sheets, since information can be encoded in the defect and not in the entire structure. Much more research will be needed before applications can be developed, however.

####

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. For more information: http://www.fapesp.br/en .

For more information, please click here

Contacts:
Joao Carlos da Silva

55-113-838-4381

Copyright © São Paulo Research Foundation (FAPESP)

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

RELATED JOURNAL ARTICLE:

Related News Press

News and information

New Method Uses DNA, Nanoparticles and Top-Down Lithography to Make Optically Active Structures: Technique could lead to new classes of materials that can bend light, such as for those used in cloaking devices January 18th, 2018

Arrowhead Pharmaceuticals Announces Pricing of Underwritten Public Offering of Common Stock January 18th, 2018

Leti to Demo New Curving Technology at Photonics West that Improves Performance of Optical Components January 18th, 2018

Arrowhead Pharmaceuticals Announces Proposed Underwritten Offering of Common Stock January 17th, 2018

Graphene/ Graphite

New catalyst for hydrogen production is a step toward clean fuel: Carbon-based nanocomposite with embedded metal ions yields impressive performance as catalyst for electrolysis of water to generate hydrogen January 16th, 2018

Study boosts hope for cheaper fuel cells: Rice University researchers show how to optimize nanomaterials for fuel-cell cathodes January 6th, 2018

Electronically-smooth '3-D graphene': A bright future for trisodium bismuthide: Electronically-smooth nature of trisodium bismuthide makes it a viable alternative to graphene/h-BN December 22nd, 2017

Magnetism

'Gyroscope' molecules form crystal that's both solid and full of motion: New type of molecular machine designed by UCLA researchers could have wide-ranging applications in technology and science January 16th, 2018

New era in high field superconducting magnets – opening new frontiers in science, nanotechnology and materials discovery January 9th, 2018

Possible Futures

New Method Uses DNA, Nanoparticles and Top-Down Lithography to Make Optically Active Structures: Technique could lead to new classes of materials that can bend light, such as for those used in cloaking devices January 18th, 2018

Arrowhead Pharmaceuticals Announces Pricing of Underwritten Public Offering of Common Stock January 18th, 2018

Leti to Demo New Curving Technology at Photonics West that Improves Performance of Optical Components January 18th, 2018

Ultra-thin optical fibers offer new way to 3-D print microstructures: Novel approach lays groundwork for using 3-D printing to repair tissue in the body January 17th, 2018

Chip Technology

Leti to Demo New Curving Technology at Photonics West that Improves Performance of Optical Components January 18th, 2018

Ultra-thin memory storage device paves way for more powerful computing January 17th, 2018

'Gyroscope' molecules form crystal that's both solid and full of motion: New type of molecular machine designed by UCLA researchers could have wide-ranging applications in technology and science January 16th, 2018

New oxide and semiconductor combination builds new device potential: Researchers integrated oxide two-dimensional electron gases with gallium arsenide and paved the way toward new opto-electrical devices January 10th, 2018

Discoveries

New Method Uses DNA, Nanoparticles and Top-Down Lithography to Make Optically Active Structures: Technique could lead to new classes of materials that can bend light, such as for those used in cloaking devices January 18th, 2018

Nanowrinkles could save billions in shipping and aquaculture Surfaces inspired by carnivorous plants delay degradation by marine fouling January 17th, 2018

Ultrathin black phosphorus for solar-driven hydrogen economy: Osaka University researchers use sunlight to make hydrogen with a new nanostructured catalyst based on nanosheets of black phosphorus and bismuth vanadate January 17th, 2018

Ultra-thin optical fibers offer new way to 3-D print microstructures: Novel approach lays groundwork for using 3-D printing to repair tissue in the body January 17th, 2018

Announcements

New Method Uses DNA, Nanoparticles and Top-Down Lithography to Make Optically Active Structures: Technique could lead to new classes of materials that can bend light, such as for those used in cloaking devices January 18th, 2018

Arrowhead Pharmaceuticals Announces Pricing of Underwritten Public Offering of Common Stock January 18th, 2018

Leti to Demo New Curving Technology at Photonics West that Improves Performance of Optical Components January 18th, 2018

Arrowhead Pharmaceuticals Announces Proposed Underwritten Offering of Common Stock January 17th, 2018

Research partnerships

Ultra-thin memory storage device paves way for more powerful computing January 17th, 2018

New catalyst for hydrogen production is a step toward clean fuel: Carbon-based nanocomposite with embedded metal ions yields impressive performance as catalyst for electrolysis of water to generate hydrogen January 16th, 2018

New era in high field superconducting magnets – opening new frontiers in science, nanotechnology and materials discovery January 9th, 2018

Touchy nanotubes work better when clean: Rice, Swansea scientists show that decontaminating nanotubes can simplify nanoscale devices January 4th, 2018

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project