Ronald Cohen primarily studies materials through first principles research—computational methods that begin with the most fundamental properties of a system, such as the nuclear charges of atoms, and then calculate what happens to a material under different conditions, such as pressure and temperature. He particularly focuses on properties of materials under extreme conditions such as high pressure and high temperature. This research applies to various topics and problems in geophysics and technological materials.

Some of his work focuses on understanding the behavior of high-technology materials called ferroelectrics—non-conducting crystals with an electric dipole moment similar to the opposite poles found in a common bar magnet. He also looks at minerals in Earth’s deep interior and of materials that display interesting physical and chemical properties. Other researchers use Cohen’s results as a tool to interpret their observations and to design experiments.

Medical imaging, sonar, semiconductors, and other electronics devices can benefit from understanding ferroelectrics. Ferroelectrics are unusual in that their polarity can exist even in the absence of an electric field, and the direction of the dipole can change when an electric field is applied. These useful substances further exhibit the piezoelectric effect—they can translate mechanical energy into electricity. New piezoelectrics have ten times the coupling between mechanical and electrical energy, and could revolutionize medical ultrasound and naval applications. Cohen investigates the physics underlying their intriguing behavior and uses theory to search for even better substances. 

 

Predicting how minerals behave at extreme pressures and temperatures in Earth’s interior is important to interpreting seismic data and to understanding the structure and dynamics of the planet. Cohen calculates what happens, for example, to iron—the major component of Earth’s core; transition metal oxides such as iron oxide (FeO), and high-pressure silicates such as MgSiO3, perovskite, alumina, and silica phases as pressure increases. Some work hones in on the temperature at Earth’s center through the computed elastic properties of iron compared with seismological data.

Cohen obtained a B.Sc. in geology from Indiana University in 1979 and a Ph.D. in geology from Harvard University in 1985. Before coming to Carnegie as a staff scientist in 1990, he was a research associate at the National Research Council from 1985-1987 and a research physicist at the Naval Research Laboratory from 1987 to 1990. For more see the Cohen lab

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Unraveling the properties of fluid metallic hydrogen could help scientists unlock the mysteries of Jupiter’s formation and internal structure. Credit: Mark Meamber, LLNL.
August 15, 2018

Washington, DC—Lab-based mimicry allowed an international team of physicists including Carnegie’s Alexander Goncharov to probe hydrogen under the conditions found in the interiors of giant planets—where experts believe it gets squeezed until it becomes a liquid metal, capable of conducting electricity. Their work is published in Science.

Hydrogen is the most-abundant element in the universe and the simplest—comprised of only a one proton and one electron in each atom. But that simplicity is deceptive, because there is still so much to learn about it, including its behavior under conditions not found on Earth.

For example, although hydrogen on the surface of giant planets,

Nitrogen is the dominant gas in Earth’s atmosphere, where it is most-commonly bonded with itself in diatomic N2 molecules. New work indicate that it becomes a metallic fluid when subjected to the extreme pressure and temperature conditions found deep insi
July 9, 2018

Washington, DC—New work from a team led by Carnegie’s Alexander Goncharov confirms that nitrogen, the dominant gas in Earth’s atmosphere, becomes a metallic fluid when subjected to the extreme pressure and temperature conditions found deep inside the Earth and other planets. Their findings are published by Nature Communications.

Nitrogen is one of the most-common elements in the universe and is crucial to life on Earth. In living organisms, it is a key part of the makeup of both the nucleic acids that form genetic material and the amino acids that make up proteins. It comprises nearly 80 percent of the Earth’s atmosphere.

But what about how nitrogen behaves in the intense

May 1, 2018

Washington, D.C.--Venkata Srinu Bhadram in Timothy Strobel’s lab at the Geophysical Laboratory (GL) will receive the ninth Postdoctoral Innovation and Excellence Award (PIE). These awards are made through nominations from the departments and are chosen by the Office of the President. The recipients are awarded a cash prize for their exceptionally creative approaches to science, strong mentoring, and contributing to the sense of campus community.

According to Strobel Venkata “is one of the best young scientists in high‐pressure research and is poised to become a world leader in the field.” Venkata started his postdoc in the Energy Frontier Research Center (EFree). EFree uses

April 17, 2018

Washington, DC—Interim Co-Presidents John Mulchaey and Yixian Zheng are thrilled to welcome experimental petrologist Michael Walter as the new Director of Carnegie's Geophysical Laboratory.  

Walter’s recent research has focused on the period early in Earth’s history, shortly after the planet accreted from the cloud of gas and dust surrounding our young Sun, when the mantle and the core first separated into distinct layers. Current topics of investigation also include the structure and properties of various compounds under the extreme pressures and temperatures found deep inside the planet, and information about the pressure, temperature, and chemical conditions of the mantle that

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The High Pressure Collaborative Access Team (HPCAT) was established to advance cutting-edge, multidisciplinary, high-pressure science and technology using synchrotron radiation at the Advanced Photon Source (APS) of Argonne National Laboratory in Illinois.

The integrated HPCAT facility has established four operating beamlines in nine hutches An array of novel X-ray diffraction—imaging at tiny scales--and spectroscopic techniques to reveal chemistry,  has been integrated with high pressure and extreme temperature instrumentation.

With a multidisciplinary approach and multi-institution collaborations, the high-pressure program at the HPCAT has enabeld myriad scientific

CDAC is a multisite, interdisciplinary center headquartered at Carnegie to advance and perfect an extensive set of high pressure and temperature techniques and facilities, to perform studies on a broad range of materials in newly accessible pressure and temperature regimes, and to integrate and coordinate static, dynamic and theoretical results. The research objectives include making highly accurate measurements to understand the transitions of materials into different phases under the multimegabar pressure rang; determine the electronic and magnetic properties of solids and fluid to multimegabar pressures and elevated temperatures; to bridge the gap between static and dynamic

The Energy Frontier Research in Extreme Environments Center (EFree) was established to accelerate the discovery and synthesis of kinetically stabilized, energy-related materials using extreme conditions. Partners in this Carnegie-led center include world-leading groups in five universities—Caltech, Cornell, Penn State, Lehigh, and Colorado School of Mines—and will use facilities built and managed by the Geophysical Laboratory at Argonne, Brookhaven, and Oak Ridge National Laboratories. Nine Geophysical Laboratory scientists will participate in the effort, along with Russell Hemley as director and Tim Strobel as associate director.

To achieve their goal, EFree personnel synthesize

The Geophysical Laboratory has made important advances in the growth of diamond by chemical vapor deposition (CVD).  Methods have been developed to produce single-crystal diamond at low pressure having a broad range of properties.

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly  Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments. 

Nick Konidaris is a staff scientist at the Carnegie Observatories and Instrument Lead for the SDSS-V Local Volume Mapper (LVM). He works on a broad range of new optical instrumentation projects in astronomy and remote sensing. Nick's projects range from experimental to large workhorse facilities. On the experimental side, he recently began working on a new development platform for the 40-inch Swope telescope at Carnegie's Las Campanas Observatory that will be used to explore and understand the explosive universe.

 Nick and his colleagues at the Department of Global Ecology are leveraging the work on Swope to develop a new airborne spectrograph that will be used to provide a direct

Experimental petrologist Michael Walter became director of the Geophysical Laboratory beginning April 1, 2018. His recent research has focused on the period early in Earth’s history, shortly after the planet accreted from the cloud of gas and dust surrounding our young Sun, when the mantle and the core first separated into distinct layers. Current topics of investigation also include the structure and properties of various compounds under the extreme pressures and temperatures found deep inside the planet, and information about the pressure, temperature, and chemical conditions of the mantle that can be gleaned from mineral impurities preserved inside diamonds.

Walter had been at

Guoyin Shen's research interests lie in the quest to establish and to examine models for explaining and controlling the behavior of materials under extreme conditions. His research activities include investigation of phase transformations and melting lines in molecular solids, oxides and metals; polyamorphism in liquids and amorphous materials; new states of matter and their emergent properties under extreme conditions; and the development of enabling high-pressure synchrotron techniques for advancing compression science. 

He obtained a Ph.D. in mineral physics from Uppsala University, Sweden in 1994 and a B.S. in geochemistry from Zhejiang University, China in 1982. For more