Superconductivity of Pressure-Stabilized Vanadium Hydrides.

The study of the high-temperature superconductive property in compressed hydrogen (H)-rich hydrides has been motivated by hydrides, which become superconducting at low pressure due to chemical precompression. In the present study, we report the first-principles structure searches for stable vanadium(V) hydrides over a pressure scope 0-200 GPa, where stable unexpected stoichiometries of H-rich V hydrides (e.g., VH3, VH5, and VH8) emerge. These dense H-rich V hydrides are metallic with a strong ionic feature, and the coordination number of metal V gradually increases with H content. In particular, C2/m-VH8, which consists of infinite zigzag chains of sole H2 molecules, has the highest coordination number of 16. From our electron-phonon calculations, one can see that P63/mmm-VH5 and C2/m-VH8 are superconductors with estimated superconducting temperatures (Tc) of 18.5 and 71.4 K at 200 GPa, respectively. Our simulations not only uncovered the crystal structures of V hydrides, but also established the high-temperature superconductive nature of them.