Ideal Strength and Emergent Superconductivity in a Three-Dimensional sp2-Carbon Network cT16

The design of carbon allotropes that simultaneously exhibit mechanical robustness and quantum functionalities remains a longstanding challenge. Here, we report a comprehensive first-principles study of cT16, a three-dimensional sp2-hybridized carbon network with topologically interlinked graphene-like sheets. The structure features high ideal tensile and shear strengths, with pronounced anisotropy arising from strain-induced bond rehybridization and interlayer slipping mechanisms. Electronic structure calculations reveal that cT16 is intrinsically metallic, with dispersive π-bands crossing the Fermi level. Phonon dispersion confirms its dynamical stability, and analysis of the Eliashberg spectral function yields a moderate electron-phonon coupling constant (λ = 0.481) and a logarithmic average frequency of 696.2 K. The superconducting transition temperature is estimated to reach 7.2 K at via the Allen-Dynes formula, without requiring any external doping or intercalation. Compared to existing carbon superconductors such as CaC6 or boron-doped diamond, cT16 uniquely combines chemical purity, structural resilience, and intrinsic superconductivity. These findings position cT16 as a promising lightweight carbon superconductor and expand the functional landscape of three-dimensional sp²-carbon frameworks.