Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Discovery of ionic elemental crystal against chemical intuition

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:
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:

More articles from Life Sciences:

nachricht Mitochondria control stem cell fate
27.10.2016 | Technische Universität München

nachricht How a fungus inhibits the immune system of plants
27.10.2016 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

The gene of autumn colours

27.10.2016 | Life Sciences

Polymer scaffolds build a better pill to swallow

27.10.2016 | Life Sciences

Greater Range and Longer Lifetime

26.10.2016 | Power and Electrical Engineering

More VideoLinks >>>