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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Carnegie Science, Carnegie Institution for Science, Carnegie Institution
January 3, 2017

Washington, DC—Germanium may not be a household name like silicon, its group-mate on the periodic table, but it has great potential for use in next-generation electronics and energy technology.

Of particular interest are forms of germanium that can be synthesized in the lab under extreme pressure conditions. However, one of the most-promising forms of germanium for practical applications, called ST12, has only been created in tiny sample sizes—too small to definitively confirm its properties.

“Attempts to experimentally or theoretically pin down ST12-germanium’s characteristics produced extremely varied results, especially in terms of its electrical conductivity,” said

Carnegie Science, Carnegie Institution, Carnegie Institution for Science
October 27, 2016

Carnegie’s Geophysical Laboratory dedicated two and a half days this week to celebrating the legacy and vision of Marilyn Fogel, who spent 33 years there doing groundbreaking research and mentoring generations of young scientists of all levels—from high school interns to postdoctoral fellows.

Fogel’s expertise in stable isotope chemistry has led to many breakthroughs in the fields of paleo-ecology, modern ecosystem studies, climate change, and astrobiology. In her honor, Geophysical Laboratory scientists and staff organized a workshop, called Marilyn Madness, which focused on the past, present, and future of isotope research.

They brought together nearly 100 of her current

October 20, 2016

Washington, DC— Did you know that there are at least 17 crystalline forms of ice, many of them formed under extreme pressures, such as those found in the interiors of frozen planets? New work from a team led by Carnegie’s Timothy Strobel has identified the structure of a new type of ice crystal that resembles the mineral quartz and is stuffed with over five weight percent of energy-rich hydrogen molecules, which is a long-standing Department of Energy goal for hydrogen storage.  

The results, published by the Journal of the American Chemical Society, could have implications for the mineralogy of icy planetary bodies as well as for energy storage technology.

As all school

October 13, 2016

Washington, DC— New work from a team led by Carnegie’s Alexander Goncharov has created a new extremely incompressible carbon nitride compound. They say it could be the prototype for a whole new family of superhard materials, due to the unexpected ratio of carbon and nitrogen atoms. Their work is published in the journal Chemistry of Materials.

Compounds that are made up of carbon and nitrogen are of great interest to materials scientists, because they can be superhard and very resistant to heat. It’s predicted that some chemical structures of carbon and nitrogen could even be harder than diamonds! If such carbon nitrides were synthesized, they could have a number of practical

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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.

Peter van Keken studies the thermal and chemical evolution of the Earth. In particularly he looks at the causes and consequences of plate tectonics; element modeling of mantle convection,  and the dynamics of subduction zones--locations where one tectonic plate slides under another. He also studies mantle plumes; the integration of geodynamics with seismology; geochemistry and mineral physics. He uses parallel computing and scientific visualization in this work.

He received his BS and Ph D from the University of Utrecht in The Netherlands. Prior to joining Carnegie he was on the faculty of the University of Michigan.

Peter Driscoll studies the evolution of Earth’s core and magnetic field including magnetic pole reversal. Over the last 20 million or so years, the north and south magnetic poles on Earth have reversed about every 200,000, to 300,000 years and is now long overdue. He also investigates the Earth’s inner core structure; core-mantle coupling; tectonic-volatile cycling; orbital migration—how Earth’s orbit moves—and tidal dissipation—the dissipation of tidal forces between two closely orbiting bodies. He is also interested in planetary interiors, dynamos, upper planetary atmospheres and exoplanets—planets orbiting other stars. He uses large-scale numerical simulations in much of his research

Andrew Newman works in several areas in extragalactic astronomy, including the distribution of dark matter--the mysterious, invisible  matter that makes up most of the universe--on galaxies, the evolution of the structure and dynamics of massive early galaxies including dwarf galaxies, ellipticals and cluster. He uses tools such as gravitational lensing, stellar dynamics, and stellar population synthesis from data gathered from the Magellan, Keck, Palomar, and Hubble telescopes.

Newman received his AB in physics and mathematics from the Washington University in St. Louis, and his MS and Ph D in astrophysics from Caltech. Before becomming a staff astronomer in 2015, he was a

Gwen Rudie studies the chemical and physical properties of very distant, so-called  high-redshift galaxies and their surrounding circumgalactic medium. She is primarily an observational astronomer working on the analysis and interpretation of high-resolution spectroscopy of high-redshift Quasi Stellar Objects and low to medium-resolution near-infrared and optical spectroscopy of high-redshift galaxies. She is interested in understanding the intergalactic medium as a tool for understanding galaxy evolution and the physical properties of very distant galaxies such as the composition of stars and their star formation rates

Rudie received her AB from Dartmouth College and her Ph D