A Structure and the Superconductivity of LiBC

Abstract

MgB2 has been found to be superconductor with a critical temperature of 39K by Akimitsu and coworkers in 2000. Then, extensive search has been made for searching similar superconductor among related intermetallic compounds. Lithium borocarbide (LiBC) is an analogue with similar structure to MgB2. In the structure of LiBC (P63/mmc), hexagonal sheets of B-C is in the place of B-B and Li is in the place of Mg contrast to MgB2. These result in the material being an insulator. LiBC is expected to be a new phonon-mediated Bardeen-Cooper-Schrieffer (BCS) superconductor. But to be this kind of superconductor, the material should be a conductor, so hole-doped method is used to make it a conductor. In the paper, a new stable structure of LiBC is discovered. Using structure prediction software CALYPSO and first principles calculation software, a new type structure of LiBC under ordinary pressure is discovered, and it has a crystal structure of <img width="30" height="15" src="http://article.sciencepublishinggroup.com/journal/606/6710005/image001.png" />. Quantum Espresso software is used to study the superconductivity of the structure, when the μ^*=0.10, election-phonon coupling parameter λ=0.4112, the critical temperature of superconductivity is 2.77 K, and the bands structure and the density of states of LiBC are obtained by the software. The structure and the superconductivity are also studied under some high pressure.