Superconductivity of Pressure-Stabilized Vanadium Hydrides

2017-11-02T15:49:32Z (GMT) by Xiaofeng Li Feng Peng
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., VH<sub>3</sub>, VH<sub>5</sub>, and VH<sub>8</sub>) 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, <i>C</i>2/<i>m</i>-VH<sub>8</sub>, which consists of infinite zigzag chains of sole H<sub>2</sub> molecules, has the highest coordination number of 16. From our electron–phonon calculations, one can see that <i>P</i>6<sub>3</sub>/<i>mmm</i>-VH<sub>5</sub> and <i>C</i>2/<i>m</i>-VH<sub>8</sub> are superconductors with estimated superconducting temperatures (<i>T</i><sub>c</sub>) 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.