Superconducting ultraincompressible hard cubic Re4C

A synthesized cubic rhenium carbide has been reported to be rock salt structured ReC (NaCl–ReC). However, our calculations indicate that not only does NaCl–ReC have larger lattice parameters than those found in experiments, it is also mechanically unstable at the ground state. In order to determine the optimal structure, rhenium carbides with different atomic stoichiometries are considered. According to the experimental data, a stable Fe4N structured Re4C (Fe4N–Re4C) for synthesized cubic rhenium carbide that is superconducting, ultraincompressible and hard is determined.