Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Oxygen molecule survives to enormously high pressures: RUB publication in Physical Review Letters

30.01.2012
RUB researcher calculates stability thresholds and structures of solid oxygen / Physical Review Letters: Oxygen as insulator, semiconductor, and metal

Using computer simulations, a RUB researcher has shown that the oxygen molecule (O2) is stable up to pressures of 1.9 terapascal, which is about nineteen million times higher than atmosphere pressure. Above that, it polymerizes, i.e. builds larger molecules or structures.


Structures of solid oxygen under high pressure: At 1.9 TPa, oxygen polymerizes and assumes a square spiral-like structure, which is semi-conducting (top). With increasing pressure, the polymer exhibits metallic properties (zig-zag chain-like phase, mid). Then, the structure changes into a metallic layer phase (bottom). The coloured areas represent the charge density in one layer of the structure. Figure: Jian Sun

“This is very surprising” says Dr. Jian Sun from the Department of Theoretical Chemistry. “Other simple molecules like nitrogen or hydrogen do not survive such high pressures.” In cooperation with colleagues from University College London, the University of Cambridge, and the National Research Council of Canada, the researcher also reports that the behaviour of oxygen with increasing pressure is very complicated. It's electrical conductivity first increases, then decreases, and finally increases again. The results are published in Physical Review Letters.

Weaker bonds, greater stability

The oxygen atoms in the O2 molecule are held together by a double covalent bond. Nitrogen (N2), on the other hand, possesses a triple bond. “You would think that the weaker double bond is easier to break than the triple bond and that oxygen would therefore polymerize at lower pressures than nitrogen” says Sun. “We found the opposite, which is astonishing at first sight.”

Coming together when pressure increases

However, in the condensed phase when pressure increases, the molecules become closer to each other. The research team suggests that, under these conditions, the electron lone pairs on different molecules repel one another strongly, thus hindering the molecules from approaching each other. Since oxygen has more lone pairs than nitrogen, the repulsive force between these molecules is stronger, which makes polymerization more difficult. However, the number of lone pairs cannot be the only determinant of the polymerization pressure. “We believe that it is a combination of the number of lone pairs and the strength of the bonds between the atoms”, says Sun.

The many structures of oxygen

At high pressures, gaseous molecules such as hydrogen, carbon monoxide, or nitrogen polymerize into chains, layers, or framework structures. At the same time they usually change from insulators to metals, i.e. they become more conductive with increasing pressure. The research team, however, showed that things are more complicated with oxygen. Under standard conditions, the molecule has insulating properties. If the pressure increases, oxygen metallises and becomes a superconductor. With further pressure increase, its structure changes into a polymer and it becomes semi-conducting. If the pressure rises even more, oxygen once more assumes metallic properties, meaning that the conductivity goes up again. The metallic polymer structure finally changes into a metallic layered structure.

Inside planets

“The polymerization of small molecules under high pressure has attracted much attention because it helps to understand the fundamental physics and chemistry of geological and planetary processes” explains Sun. “For instance, the pressure at the centre of Jupiter is estimated to be about seven terapascal. It was also found that polymerized molecules, like N2 and CO2, have intriguing properties, such as high energy densities and super-hardness.” Dr. Jian Sun joined the RUB-research group of Prof. Dr. Dominik Marx as a Humboldt Research Fellow in 2008 to work on vibrational spectroscopy of aqueous solutions. In parallel to this joint work in "Solvation Science" he developed independent research interests into high pressure chemical physics as an Early Career Researcher.

Bibliographic record

J. Sun, M. Martinez-Canales, D.D. Klug, C.J. Pickard, R.J. Needs (2012): Persistence and eventual demise of oxygen molecules at terapascal pressures, Physical Review Letters, doi: 10.1103/PhysRevLett.108.045503

Further information

Dr. Jian Sun, Department of Theoretical Chemistry, Faculty of Chemistry and Biochemistry at the Ruhr-Universität, 44780 Bochum, Tel.: +49/234/32-22121
jian.sun@theochem.rub.de

Click for more

Department of Theoretical Chemistry
http://www.theochem.rub.de/home.en.html

Editorial journalist
Dr. Julia Weiler

Dr. Josef König | idw
Further information:
http://www.theochem.rub.de/home.en.html
http://www.ruhr-uni-bochum.de

More articles from Physics and Astronomy:

nachricht NASA's OSIRIS-REx mission explains Bennu's mysterious particle events
06.12.2019 | NASA/Goddard Space Flight Center

nachricht A momentous view on the birth of photoelectrons
06.12.2019 | ETH Zurich Department of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

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

Im Focus: Developing a digital twin

University of Texas and MIT researchers create virtual UAVs that can predict vehicle health, enable autonomous decision-making

In the not too distant future, we can expect to see our skies filled with unmanned aerial vehicles (UAVs) delivering packages, maybe even people, from location...

Im Focus: The coldest reaction

With ultracold chemistry, researchers get a first look at exactly what happens during a chemical reaction

The coldest chemical reaction in the known universe took place in what appears to be a chaotic mess of lasers. The appearance deceives: Deep within that...

Im Focus: How do scars form? Fascia function as a repository of mobile scar tissue

Abnormal scarring is a serious threat resulting in non-healing chronic wounds or fibrosis. Scars form when fibroblasts, a type of cell of connective tissue, reach wounded skin and deposit plugs of extracellular matrix. Until today, the question about the exact anatomical origin of these fibroblasts has not been answered. In order to find potential ways of influencing the scarring process, the team of Dr. Yuval Rinkevich, Group Leader for Regenerative Biology at the Institute of Lung Biology and Disease at Helmholtz Zentrum München, aimed to finally find an answer. As it was already known that all scars derive from a fibroblast lineage expressing the Engrailed-1 gene - a lineage not only present in skin, but also in fascia - the researchers intentionally tried to understand whether or not fascia might be the origin of fibroblasts.

Fibroblasts kit - ready to heal wounds

Im Focus: McMaster researcher warns plastic pollution in Great Lakes growing concern to ecosystem

Research from a leading international expert on the health of the Great Lakes suggests that the growing intensity and scale of pollution from plastics poses serious risks to human health and will continue to have profound consequences on the ecosystem.

In an article published this month in the Journal of Waste Resources and Recycling, Gail Krantzberg, a professor in the Booth School of Engineering Practice...

Im Focus: Machine learning microscope adapts lighting to improve diagnosis

Prototype microscope teaches itself the best illumination settings for diagnosing malaria

Engineers at Duke University have developed a microscope that adapts its lighting angles, colors and patterns while teaching itself the optimal...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

The Future of Work

03.12.2019 | Event News

First International Conference on Agrophotovoltaics in August 2020

15.11.2019 | Event News

Laser Symposium on Electromobility in Aachen: trends for the mobility revolution

15.11.2019 | Event News

 
Latest News

Lights on fishing nets save turtles and dolphins

06.12.2019 | Ecology, The Environment and Conservation

Machine learning, imaging technique may boost colon cancer diagnosis

06.12.2019 | Life Sciences

'Virtual biopsy' allows doctors to accurately diagnose precancerous pancreatic cysts

06.12.2019 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>