Timothy Strobel subjects materials to high-pressures to understand chemical processes  and interactions, and to create new, advanced energy-related materials.

For instance, silicon is the second most abundant element in the Earth’s crust and a mainstay of the electronics industry. But normal silicon is not optimal for solar energy. In its conventional crystalline form, silicon is relatively inefficient at absorbing the wavelengths most prevalent in sunlight.  Strobel made a discovery that may turn things around.  Using the high-pressure techniques pioneered at Carnegie, he created a novel form of silicon with its atoms arranged in a cage-like structure. Unlike normal silicon, this new form has near-ideal properties for absorbing sunlight, and could potentially usher in an entirely new generation of solar cells.

Understanding the chemical reactions that can create tiny molecular cages that hold other “guest” molecules—structures called clathrates—is key to creating a new generation of electronic devices and possible energy materials.  Strobel and team are the first to use high-pressure synthesis to create a stable clathrate of sodium (Na) and silicon (Si)—the least understood system of the so-called group 14 clathrates. Strobel also created a new clathrate of hydrogen sulfide (H2S) and molecular hydrogen (H2). Both findings open the door for major advances in materials science.

In addition to these experiments, Strobel and team performed calculations to predict how the materials would behave. Calculations and experiments revealed that sodium clathrates are thermodynamically stable at high pressure. The consistency suggests that scientists can use theoretical calculations to predict new synthesis routes for other compounds.

In other work, a team including Strobel reported the synthesis of an ionic semiconductor Mg2C, under high-pressure, high-temperature conditions, which is fully recoverable to ambient conditions. Semiconductors are substances with electrical conductivity between insulators and metals used in electronic circuits.

 Strobel received his B.S. and Ph. D. from the Colorado School of Mines in 2004 and 2008 respectively. In 2008 he became a Carnegie postdoctoral fellow, where he became fascinated by high-pressure science. In 2010 he was appointed research scientist, then staff scientist in 2011. For more see the Strobel lab

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Artist's conception of lead selenide under pressure courtesy of Xiao-Jia Chen.
October 7, 2019

Washington, DC— Pressure improves the ability of materials to turn heat into electricity and could potentially be used to create clean generators, according to new work from a team that includes Carnegie’s Alexander Goncharov and Viktor Struzhkin published in Nature Materials.

Alternative energy sources are key to combating climate change caused by carbon emissions. Compounds with thermoelectric capabilities can convert thermal energy’s innate, physical need to spread from a hot place into a cold place into energy—harvesting electricity from the temperature differential. In theory, generators built from these materials could be used to recover electricity

Journal of Physical Chemistry Letters cover
September 9, 2019

Washington, DC— New materials can contribute potential solutions to many societal issues—from increasing access to clean drinking water to improving solar panel efficiency. But figuring out how to synthesize them can be a difficult process of trial and error.

Carnegie’s Li Zhu, Timothy Strobel, and Ronald Cohen have created a new tool for predicting pathways to novel materials that could speed this process up significantly. A paper demonstrating the method’s effectiveness is a cover story in The Journal of Physical Chemistry Letters.

Called PALLAS after one of the nicknames for Athena, the Greek goddess of wisdom, their method creates a kind of

March 13, 2019

Carolyn Beaumont, a senior at the Potomac School in McLean VA, won 5th place in the 78th Regeneron Science Talent Search. During the summer of 2018, she worked with Geophysical Laboratory staff members George Cody and Bjorn Mysen on a project to shed light on the molecular details of how water interacts with silicate melts. During her time, she learned how to run all aspects of the experiment, including how to operate a piston cylinder pressure apparatus that generates pressures on the order of 1.5 GPa and temperatures in excess of 1400°C. She also used molecular spectroscopy and nuclear magnetic resonance spectroscopy, to obtain detailed

September 20, 2018

A new Venture Grant has been awarded to the Geophysical Laboratory’s Dionysis Foustoukos and Sue Rhee of the Department of Plant Biology, with colleague Costantino Vetriani of Rutgers University for their project Deciphering Life Functions in Extreme Environments.

Carnegie Science Venture Grants ignore conventional boundaries and bring together cross-disciplinary researchers with fresh eyes to explore different questions. Each grant provides $100,000 support for two years with the hope for surprising outcomes. The grants are generously supported, in part, by trustee Michael Wilson and his wife Jane and by the Ambrose Monell Foundation.

Deep sea hydrothermal vents

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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.

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

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Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level.  Tracy received her Ph.D. from the California Institute of

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.