Superconductivity near the vibrational-mode instability in MgCNi3 -: art. no. 220504

To understand the role of electron-phonon interaction in superconducting MgCNi3 we have performed density-functional based linear response calculations of its lattice dynamical properties. A large coupling constant lambda=1.51 is predicted and contributing phonons are identified as displacements of Ni atoms towards octahedral interstitials of the perovskite lattice. Instabilities found for some vibrational modes emphasize the role of anharmonic effects in resolving experimental controversies.