Stability-superconductivity map for compressed Na-intercalated graphite

Abstract

A recent ab initio investigation of Na-C binary compounds under moderate pressures has uncovered a possible stable NaC${}_4$ superconductor with an estimated critical temperature up to 41K. We revisit this promising binary system by performing a more focused exploration of Na-intercalated graphite configurations, assessing the sensitivity of their thermodynamic stability to density functional approximations at different (T,P) conditions, and examining their superconducting properties with the anisotropic Migdal-Eliashberg formalism. The combinatorial screening of possible Na arrangements reveals additional stable stoichiometries, i.e., Na${}_3$C${}_{10}$, NaC${}_8$, NaC${}_{10}$, and NaC${}_{12}$, that redefine the previously proposed convex hulls for pressures up to 10 GPa. The evaluation of formation enthalpies with different van der Waals functionals indicates that the proposed compounds might not be thermodynamically stable at zero temperature but some of them could stabilize due to the vibrational entropy or form via cold compression if graphite is used as a starting material. Our more rigorous modeling of the electron-phonon coupling in NaC${}_4$ confirms the material's potential for high-temperature superconductivity, with a critical temperature reaching 48 K at 10 GPa, and reveals a well-defined two-gap structure unusual for an electron-doped compound. By tracking the position of the intercalant nearly free electron states with respect to the Fermi level in viable Na-C compounds, we map out the range of pressures and compositions needed for strong electron-phonon coupling and identify Na${}_3$C${}_{10}$ as an equally promising superconductor.

12 pages, 10 figures

References in corpus (22)

• Advanced capabilities for materials modelling with Quantum ESPRESSO
• van der Waals forces in density functional theory: The vdW-DF method
• Superconductivity in rhombohedral trilayer graphene
• Towards high-throughput superconductor discovery via machine learning
• The Stochastic Self-Consistent Harmonic Approximation: Calculating Vibrational Properties of Materials with Full Quantum and Anharmonic Effects
• New Superconducting and Semiconducting Fe-B Compounds Predicted with an Ab Initio Evolutionary Search
• Origin of superconductivity and latent charge density wave in NbS${}_2$
• Workhorse minimally-empirical dispersion-corrected density functional, with tests for weakly-bound systems: r${}^2$SCAN+rVV10
• Theoretical study of metal borides stability
• Prediction of new crystal structure phases in metal borides: a lithium monoboride analog to MgB2
• Search for ambient superconductivity in the Lu-N-H system
• General invariance and equilibrium conditions for lattice dynamics in 1D, 2D, and 3D materials
• Prediction of superconducting properties of CaB2 using anisotropic Eliashberg theory
• Possibility of superconductivity in graphite intercalated with alkaline earths investigated with density functional theory
• First-principles calculations of the superconducting properties in Li-decorated monolayer graphene within the anisotropic Migdal-Eliashberg formalism
• Anharmonic lattice dynamics via the special displacement method
• Full-bandwidth anisotropic Migdal-Eliashberg theory and its application to superhydrides
• Temperature and quantum anharmonic lattice effects on stability and superconductivity in lutetium trihydride
• $Abinitio$ study of Li-Mg-B superconductors
• Prospect of high-temperature superconductivity in layered metal borocarbides
• Thermodynamic stability of Li-B-C compounds from first principles
• Ab initio study on magnetism suppression, anharmonicity, rattling mode and superconductivity in Sc${}_{6}M$Te${}_2$ ($M$=Fe, Co, Ni)

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