Influence of aluminium substitution on phonon mediated-superconductivity in sodium host atom with carbon hexagon-like structure under varying pressure

Abstract The high-pressure phases of aluminium (Al) and sodium (Na) substituted metal carbides are investigated using the first-principles cluster expansion technique. By analysing the formation enthalpy within the convex hull of Na 1− x Al x C 2 compositions at 100 GPa, the thermodynamically stable structures of these mixtures are determined. Electronic properties are then explored to identify signs of superconductivity in the candidate phases. Notably, Na 0.1667 Al 0.8333 C 2 and Na 0.6 Al 0.4 C 2 exhibit superconductivity with critical temperatures ( T c ) of 14.7 K and 20.1 K, respectively, at varying pressures. These findings suggest the potential for T c superconductors by reducing the required pressure. At 60 GPa, Na 0.1667 Al 0.8333 C 2 shows a T c of 20.9 K, emphasising the stabilising effect of aluminium substitution under moderate pressure. These results provide insights into the exploration of superconductivity in carbon-based quantum materials with aluminium substitution and the influence of pressure.