Like at the Center of Planet Uranus: How Materials Behave Under Extreme Pressure

Jules Verne could not have dreamed of this: A research team from the University of Bayreuth, together with international partners including scientists from the University of Cologne’s Department of Chemistry, has pushed the boundaries of high-pressure and high-temperature research into cosmic dimensions. They succeeded in generating and simultaneously analyzing materials under compression pressures of more than one terapascal (1,000 gigapascals) for the first time. Such extremely high pressures prevail, for example, at the center of the planet Uranus; they are more than three times higher than the pressure at the center of the Earth. In the journal Nature, the researchers present the method they have developed for the synthesis and structural analysis of novel materials.

Breaking the Terapascal Barrier

Theoretical models predict very unusual structures and properties of materials under extreme pressure-temperature conditions. But so far, these predictions could not be verified in experiments at compression pressures of more than 200 gigapascals. On the one hand, complex technical requirements are necessary to expose material samples to such extreme pressures, and on the other hand, sophisticated methods for simultaneous structural analyses were lacking. The experiments published in Nature, therefore, open up completely new dimensions for high-pressure crystallography: materials can now be created and studied in the laboratory that exist – if at all – only under extremely high pressures in the vastness of the Universe.

“The method we have developed enables us for the first time to synthesize new material structures in the terapascal range and to analyze them in situ – that is: while the experiment is still running. In this way, we learn about previously unknown states, properties, and structures of crystals and can significantly deepen our understanding of matter in general. Valuable insights can be gained for the exploration of terrestrial planets and the synthesis of functional materials used in innovative technologies,” Professor Dr. Leonid Dubrovinsky of the Bavarian Research Institute of Experimental Geochemistry and Geophysics (BGI) at the University of Bayreuth, the lead author of the publication.

Rhenium Compounds Under Extreme Conditions

In their study, the researchers show how they have generated and visualized in situ novel rhenium compounds using the now-developed method. The compounds in question are a novel rhenium nitride (Re7N3) and a rhenium-nitrogen alloy. These materials were synthesized under extreme pressures in a two-stage diamond anvil cell heated by laser beams. Synchrotron single-crystal X-ray diffraction enabled full chemical and structural characterization.

“Rhenium-nitrogen system is full of chemical surprises. It attracted our attention several years ago, when we produced an unusual porous compound ReN₁₀ at a pressure of one million atmospheres as well as a superhard metallic conductor ReN₂ that could withstand even extremely high compression. Synthesis at one terapascal finally allowed us to get the full picture of chemical transformations, which can occur in the Re-N system at extreme conditions,” said Dr. Maxim Bykov from the Institute of Inorganic Chemistry at the University of Cologne.

“If we apply high-pressure crystallography in the terapascal range in the future, we may make further surprising discoveries in this direction. The doors are now wide open for creative materials research that generates and visualizes unexpected structures under extreme pressures,” said the study’s other lead author, Professor Dr. Natalia Dubrovinskaia from the Laboratory of Crystallography at the University of Bayreuth.

Reference: “Materials synthesis at terapascal static pressures” by Leonid Dubrovinsky, Saiana Khandarkhaeva, Timofey Fedotenko, Dominique Laniel, Maxim Bykov, Carlotta Giacobbe, Eleanor Lawrence Bright, Pavel Sedmak, Stella Chariton, Vitali Prakapenka, Alena V. Ponomareva, Ekaterina A. Smirnova, Maxim P. Belov, Ferenc Tasnádi, Nina Shulumba, Florian Trybel, Igor A. Abrikosov and Natalia Dubrovinskaia, 11 May 2022, Nature.
DOI: 10.1038/s41586-022-04550-2

Together with the Bavarian Research Institute of Experimental Geochemistry and Geophysics  (BGI) and the Laboratory of Crystallography at the University of Bayreuth, numerous other research partners were involved in the research work published in Nature: the University of Cologne, the University of Linköping, the German Electron Synchrotron DESY in Hamburg, the European Synchrotron Radiation Facility in Grenoble and the Center for Advanced Radiation Sources at the University of Chicago.