Metal Hexaborides with Sc, Ti or Mn

Ian D. R. Mackinnon, Jose A. Alarco, Peter C. Talbot

Institute for Future Environments, Brisbane, Australia.
Science and Engineering Faculty, School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Australia.

DOI: 10.4236/mnsms.2013.34023                

Abstract

Comparison of well-determined single crystal data for stoichiometric, or near-stoichiometric, metal hexaborides confirms previously identified lattice parameter trends using powder diffraction. Trends for both divalent and trivalent forms suggest that potential new forms for synthesis include Sc and Mn hexaborides. Density Functional Theory (DFT) calculations for KB₆, CaB₆, YB₆, LaB₆, boron octahedral clusters and Sc and Mn forms show that the shapes of bonding orbitals are defined by the boron framework. Inclusion of metal into the boron framework induces a reduction in energy ranging from 1 eV to 6 eV increasing with ionic charge. For metals with d₁ character, such a shift in energy brings a doubly degenerate band section along with the G-M reciprocal space direction within the conduction bands tangential to the Fermi surface. ScB₆ band structure and density of states calculations show directions and gap characteristics similar to those of YB₆ and LaB₆. These calculations for ScB₆ suggest that it may be possible to realize superconductivity in this compound if synthesized.

Keywords

Metal Hexaborides; Electronic Structure; Superconductivity; Boron Framework

Conflicts of Interest

The authors declare no conflicts of interest.

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