10 December 2018

An international research group has discovered previously unknown phases of silica, with chemical bonds and structures that should not be possible in nature. The theoretical foundation of the work has been calculated under the leadership of Igor Abrikosov, professor of theoretical physics at LiU.

Igor Abrikosov
Igor Abrikosov Photographer: Charlotte Perhammar
American scientist Linus Pauling was awarded the Nobel Prize in Chemistry in 1954 for fundamental theories concerning how different materials are constructed. These theories have allowed researchers in materials science to develop new types of material with tailored properties.

The theories that Linus Pauling developed have been shown to be fully valid, and confirmed by practical experiments – until now. A large group of physicists and materials scientists from Germany, Russia, the US and Sweden (to be precise Linköping University) has now shown, both by theoretical calculations and practical experiments, that some forms of silica exist that should not be possible, according to Linus Pauling’s theory. The result has been published in Nature Communications.

New classes of materials

“This is highly significant, since we have shown that it is possible to produce materials that we thought would be far too unstable to exist. This is completely new for me”, says Igor Abrikosov, professor in theoretical physics at Linköping University and head of the theoretical part of the research project.

“We hope that we will now be able to find completely new classes of materials with unique properties. The discovery is also significant to our understanding of the mechanical properties and processes in the Earth’s crust, and the properties that the materials acquire at high pressure”, he says.

Silicon dioxide, SiO2, also known as “quartz”, is abundant both on the Earth’s surface and in its mantle. Linus Pauling’s theories state that in the lattice of atoms in inorganic materials, the small tetrahedra of which the material consists (with compositions such as SiO2 and SiO4) are bonded at the corners (remember that a tetrahedron has sides, edges and corners). This is the normal way of forming a chemical bond, and it is the most energy-efficient.

Variants of silicon dioxide

As the pressure increases up to 30 GPa, silicon dioxide continues to form with the tetrahedra connected according to the traditional laws of chemistry. However, when the Kiseldioxid i nya faserSilicon dioxide with structures that are impossible according to traditional theories pressure is increased above 30 GPa using a diamond anvil, interesting things start to happen. In these conditions, the researchers have found variants of silicon dioxide with structures that are impossible according to traditional theories of chemical bonding. The structures they have found include SiO5 and octahedra of SiO6, where the polyhedra are bonded by sharing faces. This is the most energy-demanding way of forming a compound, and should not be possible in nature.

“Our results open a completely new pathway along which modern materials science can progress. We have shown that fundamentally new classes of material exist that arise under extreme conditions and that we thought would be chemically impossible”, says Igor Abrikosov, who has worked with Natalia Dubrovinskaia and Leonid Dubrovinsky from the Bayerisches Geoinstitut in Bayreuth for many years. Both of the latter were awarded honorary doctorates at Linköping University in 2014.

Translation George Farrants

The article: Metastable silica high pressure polymorphs as structural proxies of deep
Earth silicate melts, E. Bykova, M. Bykov, A. Černok, J. Tidholm, S. I. Simak, O. Hellman, M.P. Belov, I. A. Abrikosov, H.-P. Liermann, M. Hanfland, V. B. Prakapenka, C. Prescher, N. Dubrovinskaia, L. Dubrovinsky. Nature Communications 2018
DOI 10.1038/s41467-018-07265-z


Contact

News Theoretical Physics

Two pipettes poring liquids on to a disk.

Research for a sustainable future in ten new projects

Photosynthetic materials, two-dimensional noble metals and sustainable semiconductors are some of the projects at LiU that have been granted funding from the research programme Wallenberg initiative materials science for sustainability – WISE.

Two men in a computer server hall.

International collaboration lays the foundation for AI for materials

AI is accelerating the development of new materials. Large-scale use and exchange of data on materials is facilitated by a broad international standard. A major international collaboration now presents an extended version of the OPTIMADE standard.

LiU Theorists provide computational insight into the properties of novel ultra-incompressible, hard and superconducting W-N materials

There is an enormously growing demand for materials capable of withstanding extreme conditions, in particular advanced hard and highly electrically conducting materials.

Strategic research

Latest news from LiU

Two men in white lab coats with a computer in a lab.

Improving Alphafold to predict very large proteins

The AI tool Alphafold has been improved so that it can now predict the shape of very large and complex protein structures. Linköping University researchers have also succeeded in integrating experimental data into the tool.

Rinata Kazak looking down at her jacket.

LiU researcher ahead of UN climate summit - "I’m optimistic"

Azerbaijan will host the International Climate Summit this year. Although the country is heavily dependent on its oil production, holding the meeting there could actually be an advantage, according to Rinata Kazak, who will represent LiU.

Two women at a table talking.

Working together for a less biased world

In what ways does modern technology risk giving us a distorted picture of the world? Seeking answers, researchers at Tema Genus are working with colleagues in computer science.