Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1820512 | Physica C: Superconductivity and its Applications | 2006 | 8 Pages |
Abstract
Using first-principles, density functional theory calculations, we have shown that the increase in superconducting critical temperature to above 9Â K experimentally observed for B-rich, off-stoichiometry NbB2 material is associated with the formation of B-dimers on Nb sites rather than with the formation of Nb vacancies, as previously proposed. Our calculations show that certain of these B-dimer configurations have lower binding energies than do the vacancy structures. This result is pressure independent in the range between 0 and 10Â GPa, and above. Further, the dimer-containing materials have a higher electronic density of states at the Fermi level than do the vacancy structures. Finally, the presence of B-dimers results in the splitting off of phonon normal modes. These last two factors are relevant to the improved superconducting properties.
Related Topics
Physical Sciences and Engineering
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Condensed Matter Physics
Authors
H.H. Farrell, Randall A. LaViolette, T.M. Lillo,