Pressure-stabilized superhard superconducting clathrate borides LiYB12 and Li2YB12

Abstract

Clathrate borides have attracted great interest owing to their cagelike boron frameworks with notable properties, including oxidation resistance, exceptional hardness, and superconductivity. Here, we systematically explore the Li-Y-B system across the pressure range of 0–100 GPa through extensive computational structure searches. LiYB12 and Li2YB12, forming a unique class of clathrate borides, are predicted to be thermodynamically stable at 5 and 28 GPa, respectively. Both structures comprise B12 and B24 cages that encapsulate Li and Y atoms, respectively, corresponding to Li-doped YB12. Further, electron-phonon coupling computational simulations predict superconducting critical temperatures of ∼1K for LiYB12 and ∼2K for Li2YB12 at 50 GPa, whereas they increase to ∼2 and ∼6K at 0 GPa, respectively. In addition, both LiYB12 and Li2YB12 are superhard materials with Vickers hardness ≥40 GPa, comparable to that of YB12. These findings enrich the chemistry of boron clathrates and suggest a general strategy for designing lightweight superhard superconductors via electron doping of rigid boron-cage frameworks.

Source-reported materials — not catalogue approval

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