Electronic structures and electron–phonon superconductivity of Nb ₂ C-based MXenes

Abstract Motivated by the recent discovery of superconductivity in Nb 2 C MXene, we perform theoretical studies on both pristine and functionalized Nb 2 C using density functionals theory. First, the possible absorbing sites and structures for various functionalized groups are determined by calculating the binding energy. Second, electronic structures of Nb 2 C as well as all the functionalized systems are obtained which indicate that they are metallic. The band structures of both Nb 2 C and Nb 2 CS 2 exhibit Dirac points near the Fermi level. Last but most importantly, the lattice dynamics and electron phonon coupling (EPC) are studied for pristine and functionalized Nb 2 C. Though the EPC in Nb 2 C is weak, the functional-groups significantly enhance the EPC and thus obtain much high superconducting transition temperature ( T c ). Considering the fact that MXenes easily absorb the oxygen atoms in experiments, we suggest that the estimated T c ∼ 12 K for Nb 2 CO 2 may explain the experimentally observed T c ∼ 12.5 K for Nb 2 C.

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