Synthesis of molecular metallic barium superhydride: pseudocubic BaH12
Wuhao Chen, Dmitrii V. Semenok, Alexander G. Kvashnin, Xiaoli Huang, Ivan A. Kruglov, Michele Galasso, Hao Song, Defang Duan, Alexander F. Goncharov, Vitali B. Prakapenka, Artem R. Oganov, Tian Cui
Abstract
Abstract Following the discovery of high-temperature superconductivity in the La–H system, we studied the formation of new chemical compounds in the barium-hydrogen system at pressures from 75 to 173 GPa. Using in situ generation of hydrogen from NH 3 BH 3 , we synthesized previously unknown superhydride BaH 12 with a pseudocubic ( fcc ) Ba sublattice in four independent experiments. Density functional theory calculations indicate close agreement between the theoretical and experimental equations of state. In addition, we identified previously known P 6 /mmm -BaH 2 and possibly BaH 10 and BaH 6 as impurities in the samples. Ab initio calculations show that newly discovered semimetallic BaH 12 contains H 2 and H 3 – molecular units and detached H 12 chains which are formed as a result of a Peierls-type distortion of the cubic cage structure. Barium dodecahydride is a unique molecular hydride with metallic conductivity that demonstrates the superconducting transition around 20 K at 140 GPa.