Surface electronic structure of the nonoxide perovskite superconductor MgCNi3

I. G. Kim, J. I. Lee, A. J. Freeman

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Abstract

The surface electronic structures of MgCNi3(001) with both the MgNi terminated (MgNi-Term) and the CNi terminated (CNi-Term) surfaces were investigated using the all-electron full-potential linearized augmented plane-wave method within the generalized gradient approximation to density-functional theory. The calculated work function of MgNi-Term (4.17 eV) is lower than that of CNi-Term (5.16 eV). The number of total electrons at the surface layer of MgNi-Term is much decreased, while that of CNi-Term is less decreased than that of MgNi-Term, with respect to their center layers. The number of Ni(S) d electrons of MgNi-Term is calculated to be 0.08 electrons more than that of CNi-Term. The layer projected l-decomposed local density of states (DOS) show that the difference in the number of Ni(S)-d electrons is due to the strong C-p and Ni-d hybridization at the surface layer of CNi-Term. The peak just below the Fermi level (EF) in bulk MgCNi3 is broadened substantially at the Ni(S) of CNi-Term, while that peak survives at Ni(S) of MgNi-Term. By analyzing the charge density belonging to a very narrow energy window just below EF, such considerable modifications of the DOS peak at CNi-Term is seen to be due to the broken local symmetry of the CNi layer at the surface. It is considered that the behavior of the modification of the peak near EF resembles p-band hole doping through C-site substitution, supported by the stability against ferromagnetism determined from total-energy calculations. Superconductivity of the MgCNi3(001) surface is discussed briefly in relation with the modifications of the DOS peak at EF.

Original languageEnglish
Article number174512
Pages (from-to)1745121-1745127
Number of pages7
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume66
Issue number17
Publication statusPublished - Nov 1 2002

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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