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Superconductivity near 70 K in boron-carbon clathrates MB2C8 (M=Na, K, Rb, Cs) at ambient pressure

Bin Li, Yulan Cheng, Cong Zhu, Jie Cheng, Shengli Liu

DOI 10.1103/PhysRevB.109.184517 · Physical Review B

T1

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Abstract

Inspired by the first boron-carbon (B-C) clathrate SrB3C3 and the ternary borohydride KB2H8 [Miao et al., Phys. Rev. B 104, L100504 (2021)], we have performed first-principles density functional theory calculations of the electronic and phonon band structures for B-C compounds MB2C8 (M = Na, K, Rb, Cs). Our calculations reveal that these materials are dynamically stable and can potentially exhibit superconductivity at ambient pressure. However, only the K, Rb, and Cs compounds exhibit thermodynamic stability below 50 GPa, while NaB2C8 remains thermodynamically unstable at all pressures considered. Based on the Allen and Dynes modified McMillan equation, we predict the superconducting transition temperature Tc of these compounds to be over 65 K at ambient pressure, with Tc decreasing under higher pressures. Remarkably, we find CsB2C8 possesses the highest predicted Tc of 68.76 K. Our findings demonstrate the possibility of high temperature superconductivity in cubic MB2C8 at ambient pressure, expanding the B-C clathrate superconductor family. These results provide valuable insights to guide the identification of new atmospheric pressure superconductors.

Source-reported materials — not catalogue approval

FormulaReported Tc (K)Pressure (GPa)Type
NaB2C8

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—Pressure unresolvedunknown
KB2C8

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65Pressure unresolvedunknown
RbB2C8

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65Pressure unresolvedunknown
CsB2C8

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68.76Pressure unresolvedunknown
SrB3C3

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2223 GPaunknown
SrB3C3

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31Pressure unresolvedunknown
Rb0.5Sr0.5(BC)3

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75Pressure unresolvedunknown
KB2H8

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13412 GPaunknown
H3S

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203155 GPaunknown
LaH10

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250170 GPaunknown

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