High-pressure stability and superconductivity of vanadium hydrides*

Abstract

Using variable-composition crystal structure prediction algorithm USPEX combined with first-principles calculations, we systematically explore stable vanadium hydrides (VxHy) in the pressure range from 0 to 300 GPa. Besides reproducing all previously reported VxHy compounds, we discover three new V-rich (C222–V2H, I4/mmm-V3H2 and C222–V6H5) and three new H-rich (R-3m-V3H7, I-42m-V4H11 and Cmmm-VH11) stable phases. All stable VxHy compounds are metallic, as indicated by their electronic structures. Electron-phonon coupling calculations reveal the potential superconductive nature of VH3 (Fm-3m), VH5 (P6/mmm) and VH11 (Cmmm), with estimated critical temperature of 2.4–2.5 K for VH3, 14.5–15.5 K for VH5 and 90.9–122.6 K for VH11 at 200 GPa, respectively. Superconductivity of VH3 comes largely from coupling of the electrons with V vibrations, while in VH5 and VH11 coupling with H vibrations becomes more important as hydrogen content increases.