First-principles prediction of phonon-mediated superconductivity in XBC (X= Mg, Ca, Sr, Ba)

Abstract

From first-principles calculations, we predict four new intercalated hexagonal $X$BC ($X$=Mg, Ca, Sr, Ba) compounds to be dynamically stable and phonon-mediated superconductors. These compounds form a LiBC like structure but are metallic. The calculated superconducting critical temperature, $T{}_c$, of MgBC is 51 K. The strong attractive interaction between $\sigma$-bonding electrons and the B${}_{1g}$ phonon mode gives rise to a larger electron-phonon coupling constant (1.135) and hence high $T_c$; notably, higher than that of MgB${}_2$. The other compounds have a low superconducting critical temperature (4-17 K) due to the interaction between $\sigma$-bonding electrons and low energy phonons (E${}_{2u}$ modes). Due to their energetic and dynamic stability, we envisage that these compounds can be synthesized experimentally.

7 pages, 6 figures

References in corpus (6)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Carbon substitution in MgB2 single crystals: structural and superconducting properties
• Improved tetrahedron method for the Brillouin-zone integration applicable to response functions
• Electron-phonon coupling and superconductivity in LiB${}_{1+x}$C${}_{1-x}$

Cited by in corpus (3)

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