A group of scientists from Russia, China, and the United States predicted and then experimentally obtained barium
superhydrides' new unusual superconductors. The study was published in Nature Communications.
Chemists and physicists have been hunting down room-temperature superconductors since the first half of the 20th
century. Initially, high hopes were placed on metallic hydrogen, but solid metallic hydrogen can become superconducting
only at extremely high pressures of several million atmospheres, as it later transpired. Chemists then tried adding
other elements to hydrogen in the hope of attaining superconductivity by stabilizing the metallic state under less
challenging conditions. Scientists, including the research team led by Skoltech Professor Artem R. Oganov, predicted and
experimentally obtained a set of compounds with a huge number of hydrogen atoms, such as ThH9 and ThH10 PrH9, NdH7,
NdH9, YH6, and so on. Yet, the race for higher hydrogen content in such bizarre hydrides and especially for higher
superconducting transition temperature is still on.
In their latest study, scientists from Oganov’s laboratory and their colleagues from China and the United States
analyzed all possible barium hydrides using the unique theoretical approaches developed by Oganov and his students and
implemented in their USPEX code (http://uspex-team.org). Finally, they selected BaH12, a compound with one of the highest hydrogen contents. The researchers obtained the
compound experimentally, demonstrated its superconductivity, and studied its crystal structure. BaH12 turned out to be
quite a remarkable compound with a structure formed by molecular groups of two and three hydrogen atoms and acting as a
molecular superconductor. Thanks to its molecular structure, BaH12 is not a high-temperature superconductor: its
critical temperature is -253 degrees Celsius. The study marks significant progress in understanding what structures may
someday perform as room-temperature superconductors in real devices.
“On October 14, 2020, American scientists reported the discovery of a room-temperature superconductor, ushering in an
era of room superconductivity. The new superconductor composition has not been disclosed, but its room-temperature
superconductivity has been convincingly demonstrated. A century-long dream has come true! Recall that superconductivity
was first observed in mercury at -269 degrees Celsius over 100 years ago. The new material is unlikely to have immediate
practical applications, as it can only be synthesized in microscopic amounts under extremely high pressures of nearly
three million atmospheres. We should continue searching for new materials and studying their properties so that we could
someday figure out how to achieve room-temperature superconductivity under normal pressure,” Oganov says.