Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Discovery of ionic elemental crystal against chemical intuition

30.01.2009
An ETH Zurich researcher has developed a computational method for predicting the structure of materials.

He used it to solve the structure of a newly synthesized form of pure boron that displays some unusual physical properties and brings a surprise: it is partially ionic.

New phase of elemental boron discovered

The new structure can be viewed as a NaCl-type structure, with anionic and cationic positions occupied by two different clusters of boron atoms (B12 and B2). The difference of the electronic properties of these clusters brings about charge transfer, making this material a partially ionic boron boride (B2)?+(B12)?-. Results have been published in today's "Nature" online magazine.

Boron is the chemical element most sensitive to impurities. This enhanced sensitivity makes experimental studies of this element very difficult. However, with the discovery of a new, superhard phase of the element, the theorists and expe-rimentalists involved in the research have now come a big step closer to understanding boron. A separate publication by the authors in the "Journal of Superhard Materials" demonstrated that the new phase is superhard.

Independently synthesized

The new superhard material was independently synthesized by two researchers who eventually joined forces with crystallographer Artem Oganov's theoretical team. Initially, Jiuhua Chen, a material scientist at Florida International University, and Vladimir Solozhenko, a physical chemist at the Centre National de la Recherche Scientifique (CNRS) in France, conducted experiments on ex-tremely pure boron material, containing at most one foreign atom to one million boron atoms. They exposed this material to temperatures of over 1,500 degrees Celsius and to pressures in the range 12-30 GPa, similar to those found several hundreds of kilometers inside the Earth. Under these conditions both teams of experimentalists found a new polymorph of boron, but could not solve its structure.

New method leads to breakthrough

Artem Oganov, working at ETH Zurich's Department of Material Science, has now developed a computational method for predicting the stable crystal structu-res of materials. His calculations reveal that in the new phase, boron atoms form two different kinds of nanoclusters: an icosahedron B12 consisting of twelve atoms and dumbbell B2 consisting of just two boron atoms.

These nanoclusters are arranged in the new phase of boron just as are sodium and chlorine ions in the rock salt (table salt) structure (see diagram). The new phase is predicted to remain stable to 89 GPa. The new knowledge obtained in this study allowed the researchers to propose a phase diagram for boron - the only light element whose phase diagram remained unknown until now.

Unusual properties identified

The unexpected structure of the new phase, which the authors called gamma-B, contains atoms which are ionized, meaning that the electrons are distributed between the atoms unevenly. According to classical textbooks, ionic bonds are possible only between two different elements, such as sodium and chlorine in table salt. But in the new structure ionic bonds occur between atoms of the same element, though belonging to two kinds of nanoclusters. This ionicity leads to unusual for an element phenomena in dielectric properties, lattice dynamics, and anomalous electronic properties. Additional experiments carried out by the researchers also show that the new phase is superhard.

Oganov and his colleagues expect that forms of other elements, such as carbon heterofullerites, might display charge transfer and partial ionicity. Now a profes-sor at State University of New York at Stony Brook (USA), Oganov anticipates that sooner or later applications will be developed which are based on ionic elements. These applications could be based on switching on or off the anomalous properties (for example, strong infrared absorption) possessed by ionic elements - such properties will display dramatic changes as a result of pressure- or temperature-induced phase transitions. In addition, interesting effects related to superconductivity may appear as well.

To download an image of the newly synthesized form of pure boron, click on:
http://www.cc.ethz.ch/media/picturelibrary/news/Bor-Kristall/
ETH Zurich
ETH Zurich (Swiss Federal Institute of Technology) has a student body of fourteen thousand students from 80 nations. Nearly 360 professors teach mainly in engineering sciences and architecture, system-oriented sciences, mathematics and natural sciences, as well as carry out research that is highly valued worldwide. Distinguished by the successes of 21 Nobel laureates, ETH Zurich is committed to providing its students with unparalleled education and outstanding leadership skills.

Roman Klingler | idw
Further information:
http://www.ethz.ch
http://www.cc.ethz.ch/media/picturelibrary/news/Bor-Kristall/

More articles from Life Sciences:

nachricht Building a brain, cell by cell: Researchers make a mini neuron network (of two)
23.05.2018 | Institute of Industrial Science, The University of Tokyo

nachricht Research reveals how order first appears in liquid crystals
23.05.2018 | Brown University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Research reveals how order first appears in liquid crystals

23.05.2018 | Life Sciences

Space-like gravity weakens biochemical signals in muscle formation

23.05.2018 | Life Sciences

NIST puts the optical microscope under the microscope to achieve atomic accuracy

23.05.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>