Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Geosciences Professor Predicts Stable Compounds of Oxygen and “Inert” Gas Xenon

13.11.2012
An international team led by Artem R. Oganov, PhD, a professor of theoretical crystallography in the Department of Geosciences and Department of Physics and Astronomy at Stony Brook University, has established stability of several oxides of normally inert xenon.

These compounds are predicted to be stable at high pressures above 830,000 atmospheres, i.e. at pressures corresponding to the Earth’s mantle and readily achievable in the laboratory. The results of their work, "Xenon oxides and silicates at high pressures,” were published November 11 in Nature Chemistry(1)

Dr. Oganov and his team used Oganov’s novel method for crystal structure prediction, which allowed them to find optimal structures and compositions of new compounds at any given pressure. In this work, they applied it to finding stable xenon oxides and silicates.

It has earlier been suggested that xenon oxides or silicates are formed in Earth’s interior, and prevent xenon from escaping into the atmosphere – thus explaining the “missing xenon paradox”, i.e. the observed order-of-magnitude depletion of xenon in the atmosphere.

“Xenon has to be stored in Earth’s mantle, otherwise we would have to admit that the existing chemical models of the Earth are deficient, probably as a result of an unknown cosmochemical process that removed xenon from the Earth,” said Oganov. “We have found that while xenon silicates cannot be stable at pressures of the Earth’s mantle, xenon oxides do become stable at these conditions.

However, these are extremely strong oxidants and cannot exist in the reducing environment of the Earth’s deep mantle. Our work, however, suggest another possibility – since strong Xe-O bonds can be formed under pressure, xenon atoms can be trapped and retained by defects and grain boundaries of mantle minerals, and our simulations give suggestions for local geometries of such trapping sites.”

In addition to solving an important geological puzzle, present results shed light on the still elusive chemistry of xenon. The very possibility of xenon, an inert gas, to form stable chemical compounds with fluorine and oxygen, was proposed theoretically by Pauling in 1932 and verified in 1962 in landmark experiments by Neil Bartlett.

However, only xenon fluorides were found to be thermodynamically stable; xenon oxides turned out to be unstable to decomposition into xenon and oxygen, with some decomposing explosively. The work of Oganov’s group for the first time finds stable xenon oxides, and concludes that high pressure is necessary for their stability.

The new structures are very rich in chemistry: with increasing pressure, increasing oxidation states of xenon are found, from +2 to +4 to +6. Predictions include some very unusual structures; for example, the P42/mnm phase of XeO3 contains linear chains of O2 molecules, which partially dissociate on increasing pressure. The authors found a very clear electronic signature of different valence states of xenon in different structures – something that could pave the way for new advances in the theory of chemical bonding. Another surprise was the unexpectedly high (50%) degree of ionicity in these semiconducting compounds.

“Chemical bonding appears to be simpler than expected by many,” said graduate student Qiang Zhu, the lead author of this paper. “You don’t need to invoke d-orbitals and exotic types of hybridization of Xe atoms. Bonding is significantly ionic; valence states differ by the number of p-electrons removed from Xe atoms, and pressure is essential for enabling such significantly ionic bonding”. Pressure-induced ionization, observed in many other compounds and even pure elements, appears to soften interatomic repulsions.

“In addition to providing a likely solution to the missing xenon paradox and clarifying essential aspects of xenon chemistry, our study may result in practical applications,” says Oganov. “For example, the ability of xenon to form strong chemical bonds with oxygen and other elements, and to be trapped in crystalline defects, suggests their use as non-classical luminescence centers and active sites for catalysis”.

(1) Zhu Q., Jung D.Y., Oganov A.R., Glass C.W., Gatti C., Lyakhov A.O. Stability of xenon oxides at high pressures. Nature Chemistry doi:10.1038/nchem.1497 (2012). http://www.nature.com/nchem/journal/vaop/ncurrent/pdf/nchem.1497.pdf

Artem R. Oganov | Newswise Science News
Further information:
http://www.stonybrook.edu

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New bioimaging technique is fast and economical

21.08.2017 | Medical Engineering

Silk could improve sensitivity, flexibility of wearable body sensors

21.08.2017 | Materials Sciences

On the way to developing a new active ingredient against chronic infections

21.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>