Electronic structure and magnetism in superconductor ZnNNi3: A comparative study with ZnCNi3 and ZnNi3

We have investigated the structural, electronic, and magnetic properties of a newly discovered antiperovskite superconductor ZnNNi3 and related compounds ZnCNi3 and ZnNi3 by using full-potential linearized augmented plane-wave method with the generalized gradient approximation (GGA). It is found that the electronic structures of ZnNNi3 and ZnCNi3 are very similar, existing a characteristic density of states (DOS) peak just below the Fermi level, which is dominated by Ni d bands with a small contribution from N/C p states. Contrarily, the band structure and Fermi surface in ZnNi3 is changed considerably. Based on the free electron model, the Sommerfeld coefficients and the molar Pauli paramagnetic susceptibility for these compounds are evaluated. The spin-polarized calculations and the fixed spin-moment calculations indicate that both ZnNNi3 and ZnCNi3 are not near magnetism, while ZnNi3 shows a typically ferromagnetic behavior. Furthermore, we also investigated the influence of N/C-defect on the electronic and magnetic properties. We found that ZnCNi3 is more sensitive to the defect than ZnNNi3, which well explains the fact why superconductivity has not yet been observed in ZnCNi3.