Emergent superconductivity upon electron delocalization in layered nitride VCaN₂ at ambient pressure

Electrides hosting localized interstitial anionic electrons (IAEs) offer a unique platform for emergent quantum phenomena: the delocalization of these electrons can transform the electronic landscape and potentially induce superconductivity. Here, we use first-principles calculations to predict phonon-mediated superconductivity with a critical temperature (T_c) up to 43 K at ambient pressure in the layered ternary nitride VCaN₂ (relative to 7.5 K in the binary VN). This compound is derived from the electride parent WCaN₂via substitution of V for W. The substitution triggers two concurrent effects: a rigid band shift of approximately 1.9 eV that precisely places a high density of states (DOS) near the Fermi level (E_F), and a complete depletion of the IAEs that characterizes the electride state. Crucially, the DOS peak, originating predominantly from V-3d orbitals yields a strong electron-phonon coupling (EPC) strength (λ = 1.217) primarily mediated by low-frequency V vibrational modes. By solving the anisotropic Migdal-Eliashberg equations, the calculated superconducting gap is found to vanish at 43 K under ambient pressure. Notably, the disappearance of IAEs upon V substitution signals a transition from localized to delocalized electronic states, which accompanies and facilitates the emergence of metallicity. Electronic localization function (ELF) calculations quantitatively confirm this loss of electride character. Our findings establish VCaN₂ as a rare ambient-pressure nitride superconductor exceeding the McMillan limit with high-T_c phonon-mediated superconductivity in layered electride-derived materials.