Scientists discover new properties of uranium compounds

Scientists from Russia, China and the United States have predicted and experimentally experimented with the identification of new uranium hydrides, predicting superconductivity for some of them. The results of their study were published in Progress of science.

The phenomenon of superconductivity was discovered in 1911 by a group of scientists led by the Dutch physicist Heike Kamerlingh Onnes. Superconductivity means the complete disappearance of the electrical resistance in a material when it is cooled to a specific temperature, which forces the magnetic field to come out of the material. At first, superconductivity was discovered in some base metals such as aluminum and mercury at temperatures of several degrees above absolute zero, which corresponds to -273 ° C. Scientists are particularly interested in the high temperature superconductors which exhibit superconductivity at less extreme temperatures. The superconductors at the highest temperature operate at -183 ° C and therefore require constant cooling. In 2015, a rare sulfur hydride (H₃S) sets a new high-temperature superconductivity record of -70 ° C, although at pressures up to 1,500,000 atm.

A group of physicists led by Professor Artem R. Oganov predicted that much lower pressures of about 50,000 atmospheres could produce 14 new uranium hydrides, of which only one, UH3, was known to date . They include hydrogen-rich compounds, such as UH7 and UH8, which scientists have also predicted to be superconductors. Many of these compounds were then obtained from the experiments conducted by the teams of Prof. Alexander Goncharov of the Carnegie Institute of Washington, USA, and the Institute of Solid State Physics of the Chinese Academy of Sciences. science. Calculations suggest that the superconductor at the highest temperature is UH7, which displays a superconducting capacity at -219 ° C – a temperature level that can be further increased by doping.

"After H₃S was discovered, scientists began to look for superconducting hydrides in other non-metals, such as selenium, phosphorus, etc. Our study has shown that metal hydrides have as much potential as non-metals in terms of high-temperature superconductivity "lead author of the study Ivan Kruglov, a researcher at the MIPT's Computer Materials Discovery Lab.

"The two strengths of our results are that high pressure produces an incredibly rich collection of hydrides, most of which are not part of classical chemistry, and that these hydrides can actually be obtained and become superconductors. at very low pressure, maybe even at atmospheric pressure., "says Artem Oganov.

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More information:
Ivan A. Kruglov et al. Moderate pressure uranium polyhydrides: prediction, synthesis and expected superconductivity, Progress of science (2018). DOI: 10.1126 / sciadv.aat9776