Electronic structures of antiperovskite superconductors MgXNi3 (X = B, C, and N)

Abstract

We have investigated electronic structures of a newly discovered antiperovskite superconductor MgCNi3 and related compounds MgBNi3 and MgNNi3. In MgCNi3, a peak of very narrow and high density of states is located just below the Fermi level. which corresponds to the pi* antibonding state of Ni 3d and C 2p but with the predominant Ni 3d character. The prominent nesting feature is observed in the Gamma -centered electron Fermi surface of an octahedron-cage-like shape that originates from the 19th band. The estimated superconducting parameters are in reasonable agreement with experiment, suggesting that the superconductivity in MgCNi3 is described properly by the conventional BCS phonon mechanism.