Electronic structures and electron-phonon superconductivity of Nb2C-based MXenes

Motivated by the recent discovery of superconductivity in Nb2C MXene, we perform theoretical studies on both pristine and functionalized Nb2C 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 Nb2C as well as all the functionalized systems are obtained which indicate that they are metallic. The band structures of both Nb2C 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 Nb2C. Though the EPC in Nb2C 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 estimatedT(c)similar to 12 K for Nb(2)CO(2)may explain the experimentally observedT(c)similar to 12.5 K for Nb2C.