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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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

April 15, 2020

Washington, DC— Carnegie mineralogist Robert Hazen was inducted last month as a foreign member of the Russian Academy of Sciences—the nation’s highest-level scientific society, originally founded by Peter the Great. This is a rare honor for an American researcher.

The ceremony, originally scheduled for the end of March, was postponed by the COVID-19 pandemic.

A Staff Scientist at Carnegie’s Earth and Planets Laboratory, Hazen pioneered the concept of mineral evolution—linking an explosion in mineral diversity to the rise of life on Earth—and developed  the idea of mineral ecology—which analyzes the spatial distribution of the

Carbon-boron clathrate cage with strontium inside, courtesy Tim Strobel
January 10, 2020

Washington, DC— A long-sought-after class of “superdiamond” carbon-based materials with tunable mechanical and electronic properties was predicted and synthesized by Carnegie’s Li Zhu and Timothy Strobel. Their work is published by Science Advances.

Carbon is the fourth-most-abundant element in the universe and is fundamental to life as we know it. It is unrivaled in its ability to form stable structures, both alone and with other elements.

A material’s properties are determined by how its atoms are bonded and the structural arrangements that these bonds create. For carbon-based materials, the type of bonding makes the difference between the

December 16, 2019

Washington, DC— Every school child learns about the water cycle—evaporation, condensation, precipitation, and collection. But what if there were a deep Earth component of this process happening on geologic timescales that makes our planet ideal for sustaining life as we know it?

New work published in the Proceedings of the National Academy of Sciences by Carnegie’s Yanhao Lin and Michael Walter—along with former Carnegie scientists and ongoing collaborators Ho-Kwang “Dave” Mao and Qingyang Hu of the Center for High Pressure Science and Technology Advanced Research Shanghai and Yue Meng of Argonne National Laboratory—demonstrates that a key

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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.

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

Phillip Cleves’ Ph.D. research was on determining the genetic changes that drive morphological evolution. He used the emerging model organism, the stickleback fish, to map genetic changes that control skeletal evolution. Using new genetic mapping and reverse genetic tools developed during his Ph.D., Cleves identified regulatory changes in a protein called bone morphogenetic protein 6 that were responsible for an evolved increase in tooth number in stickleback. This work illustrated how molecular changes can generate morphological novelty in vertebrates.

Cleves returned to his passion for coral research in his postdoctoral work in John Pringles’ lab at Stanford

Brittany Belin joined the Department of Embryology staff in August 2020. Her Ph.D. research involved developing new tools for in vivo imaging of actin in cell nuclei. Actin is a major structural element in eukaryotic cells—cells with a nucleus and organelles —forming contractile polymers that drive muscle contraction, the migration of immune cells to  infection sites, and the movement of signals from one part of a cell to another. Using the tools developed in her Ph.D., Belin discovered a new role for actin in aiding the repair of DNA breaks in human cells caused by carcinogens, UV light, and other mutagens.

Belin changed course for her postdoctoral work, in

Evolutionary geneticist Moises Exposito-Alonso joined the Department of Plant Biology as a staff associate in September 2019. He investigates whether and how plants will evolve to keep pace with climate change by conducting large-scale ecological and genome sequencing experiments. He also develops computational methods to derive fundamental principles of evolution, such as how fast natural populations acquire new mutations and how past climates shaped continental-scale biodiversity patterns. His goal is to use these first principles and computational approaches to forecast evolutionary outcomes of populations under climate change to anticipate potential future