First-principles prediction of superconductivity in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>MgB</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">C</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>
Truong-Tho Pham, Duc‐Long Nguyen
Abstract
From first-principles density functional theory calculations, we propose hexagonal layered ${\mathrm{MgB}}_{3}{\mathrm{C}}_{3}$ as a potential phonon-mediated superconductor at 59 K, which is far higher than the superconductivity of ${\mathrm{MgB}}_{2}$ ($\ensuremath{\approx}$ 39 K). The ${\mathrm{MgB}}_{3}{\mathrm{C}}_{3}$ is energetically and dynamically stable at ambient pressure in the P-62m hexagonal structure with c/a $\ensuremath{\approx}$ 0.79 and forms in stacks of honeycomb B-C layers with Mg as a space filler. Band structure calculations indicate that the bands at the Fermi level derive mainly from B and C orbitals in which two $\ensuremath{\sigma}$ and two $\ensuremath{\pi}$ bands both contribute to the total density of state. The $\ensuremath{\pi}$ bands are found to be strongly coupled with out-of-plane acoustic phonon mode, while the $\ensuremath{\sigma}$ bands coupled with the in-plane bond-stretching optical ${\mathrm{E}}^{\ensuremath{'}}$ phonon modes produces a sizable superconductivity in ${\mathrm{MgB}}_{3}{\mathrm{C}}_{3}$.