First-principles design of ambient-pressure MgxB2C2 and NaxBC superconductors

Abstract

We employ ab initio modeling to investigate the possibility of attaining high-temperature conventional superconductivity in ambient-pressure materials based on the known MgB2C2 and recently proposed thermodynamically stable NaBC ternary compounds. The constructed (T,PM) phase diagrams (M = Mg or Na) indicate that these layered metal borocarbides can be hole doped via thermal deintercalation that has been successfully used in previous experiments to produce Li1>x≳0.5BC samples. The relatively low temperature threshold required to trigger NaBC desodiation may help prevent the formation of defects shown recently to be detrimental to the electron-phonon coupling in the delithiated LiBC analog. According to our numerical solutions of the anisotropic full-bandwidth Migdal-Eliashberg equations, the proposed MgxB2C2 and NaxBC materials exhibit superconducting critical temperatures between 43 K and 84 K. At the same time, we demonstrate that buckling of defect-free honeycomb BC layers, favored in heavily doped NaxBC compounds, can substantially reduce or effectively suppress the materials' potential for MgB2-type superconductivity.

Source-reported materials — not catalogue approval

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