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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Fullerene C60 purchased from Shutterstock
November 24, 2021

Washington, DC—Carnegie’s Yingwei Fei and Lin Wang were part of an international research team that synthesized a new ultrahard form of carbon glass with a wealth of potential practical applications for devices and electronics. It is the hardest known glass with the highest thermal conductivity among all glass materials. Their findings are published in Nature.

Function follows form when it comes to understanding the properties of a material. How its atoms are chemically bonded to each other, and their resulting structural arrangement, determines a material’s physical qualities—both those that are observable by the naked eye and those that are only revealed

Silicon in the periodic table courtesy of Shutterstock
June 3, 2021

Washington, DC—A team led by Carnegie’s Thomas Shiell and Timothy Strobel developed a new method for synthesizing a novel crystalline form of silicon with a hexagonal structure that could potentially be used to create next-generation electronic and energy devices with enhanced properties that exceed those of the “normal” cubic form of silicon used today.

Their work is published in Physical Review Letters.

Silicon plays an outsized role in human life. It is the second most abundant element in the Earth’s crust. When mixed with other elements, it is essential for many construction and infrastructure projects. And in pure elemental form, it is

CLIPPIR diamonds by Robert Weldon, copyright GIA, courtesy Gem Diamonds Ltd.
March 31, 2021

Washington, DC— Diamonds that formed deep in the Earth’s mantle contain evidence of chemical reactions that occurred on the seafloor. Probing these gems can help geoscientists understand how material is exchanged between the planet’s surface and its depths.  

New work published in Science Advances confirms that serpentinite—a rock that forms from peridotite, the main rock type in Earth’s mantle, when water penetrates cracks in the ocean floor—can carry surface water as far as 700 kilometers deep by plate tectonic processes.

“Nearly all tectonic plates that make up the seafloor eventually bend and slide down into the mantle

Stock image of the transition metals section of the periodic table
July 1, 2020

Washington, DC— You’ve heard the expression form follows function? In materials science, function follows form.

New research by Carnegie’s Olivier Gagné and collaborator Frank Hawthorne of the University of Manitoba categorizes the causes of structural asymmetry, some surprising, which underpin useful properties of crystals, including ferroelectricity, photoluminescence, and photovoltaic ability. Their findings are published this week as a lead article in the International Union of Crystallography Journal.

“Understanding how different bond arrangements convey various useful attributes is central to the materials sciences” explained

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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.

Ana Bonaca is Staff Member at Carnegie Observatories. Her specialty is stellar dynamics and her research aims to uncover the structure and evolution of our galaxy, the Milky Way, especially the dark matter halo that surrounds it. In her research, she uses space- and ground-based telescopes to measure the motions of stars, and constructs numerical experiments to discover how dark matter affected them.

She arrived in September 2021 from Harvard University where she held a prestigious Institute for Theory and Computation Fellowship. 

Bonaca studies how the uneven pull of our galaxy’s gravity affects objects called globular clusters—spheres made up of a million

Peter Gao's research interests include planetary atmospheres; exoplanet characterization; planet formation and evolution; atmosphere-surface-interior interactions; astrobiology; habitability; biosignatures; numerical modeling.

His arrival in September 2021 continued Carnegie's longstanding tradition excellence in exoplanet discovery and research, which is crucial as the field prepares for an onslaught of new data about exoplanetary atmospheres when the next generation of telescopes come online.

Gao has been a part of several exploratory teams that investigated sulfuric acid clouds on Venus, methane on Mars, and the atmospheric hazes of Pluto. He also

Anne Pommier's research is dedicated to understanding how terrestrial planets work, especially the role of silicate and metallic melts in planetary interiors, from the scale of volcanic magma reservoirs to core-scale and planetary-scale processes.

She joined Carnegie in July 2021 from U.C. San Diego’s Scripps Institution of Oceanography, where she investigated the evolution and structure of planetary interiors, including our own Earth and its Moon, as well as Mars, Mercury, and the moon Ganymede.

Pommier’s experimental petrology and mineral physics work are an excellent addition to Carnegie’s longstanding leadership in lab-based mimicry of the

Johanna Teske became the first new staff member to join Carnegie’s newly named Earth and Planets Laboratory (EPL) in Washington, D.C., on September 1, 2020. She has been a NASA Hubble Fellow at the Carnegie Observatories in Pasadena, CA, since 2018. From 2014 to 2017 she was the Carnegie Origins Postdoctoral Fellow—a joint position between Carnegie’s Department of Terrestrial Magnetism (now part of EPL) and the Carnegie Observatories.

Teske is interested in the diversity in exoplanet compositions and the origins of that diversity. She uses observations to estimate exoplanet interior and atmospheric compositions, and the chemical environments of their formation