Geoscientists predict new compounds change our view of what planets are made of

Structures of the newly predicted magnesium oxides: On the left, MgO2; on the right, Mg3O2. Green – Mg atoms, red – O atoms. Isosurfaces show regions of high electron localization.

A team of researchers led by Artem R. Oganov, a professor of theoretical crystallography in the Department of Geosciences, Stony Brook University, has made a startling prediction that challenges existing chemical models and current understanding of planetary interiors—magnesium oxide, a major material in the formation of planets, can exist in several different compositions.

Artem R. Oganov

The team's findings, "Novel stable compounds in the Mg-O system under high pressure," are published in the online edition of Physical Chemistry Chemical Physics.

The existence of these compounds—which are radically different from traditionally known or expected materials—could have important implications.

"For decades it was believed that MgO is the only thermo-dynamically stable magnesium oxide, and it was widely believed to be one of the main materials of the interiors of the Earth and other planets," said Qiang Zhu, the lead author of this paper and a postdoctoral student in the Oganov laboratory.

"We have predicted that two new compounds, MgO2 and Mg3O2, become stable at pressures above one and five million atmospheres, respectively. This not only overturns standard chemical intuition but also implies that planets may be made of totally unexpected materials. We have predicted conditions (pressure, temperature, oxygen fugacity) necessary for stability of these new materials, and some planets, though probably not the Earth, may offer such conditions," added Oganov.

In addition to their general chemical interest, MgO2 and Mg3O2 might be important planet-forming minerals in deep interiors of some planets. Planets with these compounds would most likely be the size of Earth or larger.

Qiang Zhu

The team explained how its paper predicted the structures in detail by analysing the electronic structure and chemical bonding for these compounds. For example, Mg3O2 is forbidden within "textbook chemistry," where the Mg ions can only have charges "+2," O ions are "-2, and the only allowed compound is MgO.

In the "oxygen-deficient" semiconductor Mg3O2, there are strong electronic concentrations in the "empty space" of the structure that play the role of negatively charged ions and stabilize this material.

Curiously, magnesium becomes a d-element (i.e. a transition metal) under pressure, and this almost alchemical transformation is responsible for the existence of the "forbidden" compound Mg3O2.

The findings were made using unique methods of structure prediction, developed in the Oganov laboratory.

"These methods have led to the discovery of many new phenomena and are used by a number of companies for systematically discovering novel materials on the computer—a much cheaper route, compared to traditional experimental methods," said Zhu.

"It is known that MgO makes up about 10 percent of the volume of our planet, and on other planets this fraction can be larger. The road is now open for a systematic discovery of new unexpected planet-forming materials," concluded Oganov.

More information: 
Zhu Q., Oganov A.R., Lyakhov A.O. (2013). Novel stable compounds in the Mg-O system under high pressure. Phys. Chem. Chem. Phys., in press. pubs.rsc.org/en/content/articlelanding/2013/cp/c3cp50678a

Brain Scans: Predicting Future Criminal Behavior?

A new study shows that neuroimaging data can predict the likelihood of whether a criminal will reoffend following release from prison. 

Credit: © jinga80 / Fotolia

The paper, which is to be published in the Proceedings of the National Academy of Sciences (PNAS), studied impulsive and antisocial behaviour and centered on the anterior cingulate cortex (ACC), a portion of the brain that deals with regulating behavior and impulsivity.

The study demonstrated that inmates with relatively low anterior cingulate activity were twice as likely to reoffend than inmates with high-brain activity in this region.

Dr Kent Kiehl

"These findings have incredibly significant ramifications for the future of how our society deals with criminal justice and offenders," said Dr Kent Kiehl, who was senior author on the study and is director of mobile imaging at MRN and an associate professor of psychology at the University of New Mexico.

"Not only does this study give us a tool to predict which criminals may reoffend and which ones will not reoffend, it also provides a path forward for steering offenders into more effective targeted therapies to reduce the risk of future criminal activity."

The study looked at 96 adult male criminal offenders aged 20-52 who volunteered to participate in research studies.

This study population was followed over a period of up to four years after inmates were released from prison.

Walter Sinnott-Armstrong

"These results point the way toward a promising method of neuroprediction with great practical potential in the legal system," said Dr. Walter Sinnott-Armstrong, Stillman Professor of Practical Ethics in the Philosophy Department and the Kenan Institute for Ethics at Duke University, who collaborated on the study.

"Much more work needs to be done, but this line of research could help to make our criminal justice system more effective."

The study used the Mind Research Network's Mobile Magnetic Resonance Imaging (MRI) System to collect neuroimaging data as the inmate volunteers completed a series of mental tests.

"People who reoffended were much more likely to have lower activity in the anterior cingulate cortices than those who had higher functioning ACCs," Kiehl said.

"This means we can see on an MRI a part of the brain that might not be working correctly -- giving us a look into who is more likely to demonstrate impulsive and anti-social behavior that leads to re-arrest."

"The anterior cingulate cortex of the brain is "associated with error processing, conflict monitoring, response selection, and avoidance learning," according to the paper.

"People who have this area of the brain damaged have been shown to produce changes in 'dis-inhibition' (the inability to be inhibited by their socially unacceptable actions), apathy, and aggressiveness. "

"Indeed, ACC-damaged patients have been classed in the 'acquired psychopathic personality' genre." Kiehl says he is working on developing treatments that increase activity within the ACC to attempt to treat the high-risk offenders.

Reference
Neuroprediction of future rearrest. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1219302110

Canadian Physicists predict cooler computers

Canadian physicists say they have discovered new behaviours of light occurring within photonic crystals.

University of Toronto quantum optics researchers Professor Sajeev John and doctoral student Xun Ma said their findings could lead to faster optical information processing and compact computers that don't overheat.

"We discovered that by sculpting a unique artificial vacuum inside a photonic crystal, we can completely control the electronic state of artificial atoms within the vacuum," Ma, lead author of the study, said. "This discovery can enable photonic computers that are more than 100 times faster than their electronic counterparts, without heat dissipation issues and other bottlenecks currently faced by electronic computing."

John said he and Ma designed a vacuum in which light passes through circuit paths whose character changes drastically and abruptly with the wave length of the light.

"A vacuum experienced by light is not completely empty, and can be made even emptier," said John. "It's not the traditional understanding of a vacuum."

Ma added: "In this vacuum, the state of each atom -- or quantum dot -- can be manipulated with color-coded streams of laser pulses that sequentially excite and de-excite it in trillionths of a second. These quantum dots can in turn control other streams of optical pulses, enabling optical information processing and computing."

The research is reported in the journal Physical Review Letters.