Coexistence of covalent and metallic bonding in the boron intercalation superconductor MgB₂

Authors

Kirill D. Belashchenko, University of Nebraska-LincolnFollow
Mark van Schilfgaarde, Sandia National LaboratoriesFollow
Vladimir P. Antropov, Iowa State UniversityFollow

Date of this Version

8-2-2001

Comments

Published in PHYSICAL REVIEW B, VOLUME 64, 092503. © 2001 American Physical Society. Used by permission.

Abstract

Chemical bonding and electronic structure of MgB₂, a boron-based newly discovered superconductor, is studied using self-consistent band-structure techniques. Analysis of the transformation of the band structure for the hypothetical series of graphite–primitive graphite–primitive graphitelike boron–intercalated boron, shows that the band structure of MgB₂ is graphitelike, with π bands falling deeper than in ordinary graphite. These bands possess a typically delocalized and metallic, as opposed to covalent, character. The in-plane σ bands retain their two-dimensional (2D) covalent character, but exhibit a metallic hole-type conductivity. The coexistence of 2D covalent in-plane and three-dimensional (3D) metallic-type interlayer conducting bands is a peculiar feature of MgB₂. We analyze the 2D and 3D features of the band structure of MgB₂ and related compounds, and their contributions to conductivity.