Pressure-induced superconductivity in hypercoordinated 5p-block element nitrides MN6 (M = Sb, Te, I)

The recent studies of high-pressure synthesis and stabilization of a variety of polynitrogens have had an immense impact on nitrogen chemistry. However, the metallization and superconductivity of solid nitrogen at high pressure have not yet been verified. Here, based on first-principles calculations, we report a remarkable finding of the metallic N6 hexazine ring stabilized in the 5p -block element nitrides MN6 (M = Sb, Te, I) at an experimentally accessible pressure of 100 GPa. Strikingly, the 5p -block elements act as precompressors and electron donors for the N sublattice, leading to the Jahn-Teller distortion of the N6 hexazine ring and endowing the 5p -block element nitrides superconductivity with a high superconducting critical temperature (T c) of up to 36.8 K, close to the McMillan limit (40 K). This is the first discovery of a nitrogen-based superconductor with distorted N6 hexazine rings. The high T c is attributed to the strong electron-phonon coupling that is induced by the phonon softening and the hybridized electronic states between N and 5s and 5p orbitals of 5p -block elements. Our works have broad implications for enriching novel p -block element nitrides and nitrogen chemistry under extreme conditions.