Electronic Structures of Antiperovskite Superconductor MgCNi3and Related Compounds

Electronic structure of a newly discovered antiperovskite superconductorMgCNi$_3$ is investigated by using the LMTO band method. The main contributionto the density of states (DOS) at the Fermi energy $E_{\rm F}$ comes from Ni3$d$ states which are hybridized with C 2$p$ states. The DOS at $E_{\rm F}$ isvaried substantially by the hole or electron doping due to the very high andnarrow DOS peak located just below $E_{\rm F}$. We have also exploredelectronic structures of C-site and Mg-site doped MgCNi$_3$ systems, anddescribed the superconductivity in terms of the conventional phonon mechanism.