Ambient-pressure hardness and superconductivity in sp2 and sp3 bonded Ce−B compounds

Abstract

Stimulated by recent experimental synthesis efforts of LaB8, WB2, and α−MoB2, all characterized by intrinsic superconductivity (SC), we investigated the introduction of cerium (Ce) into various boron (B) concentrations by leveraging first-principles calculations in tandem with crystal-structure prediction techniques. Under ambient and external pressure, Ce atoms transfer electrons to B atoms, enabling the formation of distinct B configurations, namely honeycomb-like B layers in CeB, honeycomb-like B layers in CeB2, B20 cages in CeB5, B24 cages in CeB6, B23 cages in CeB7, B26 cages in CeB8, and B24 cages in CeB12. Except for CeB5 and CeB7, the other Ce-B compounds can be quenched to ambient pressure. Clathrate-like CeBn (n=6, 8, and 12) compounds hold promising prospects as potential incompressible materials, with Vickers hardness (Hv) of 20∼39 GPa. Based on the Migdal-Eliashberg (ME) theory, we discovered that both CeB2 and CeB8 are typical anisotropic single-gap superconductors with superconducting critical temperature (Tc) values of 29 and 27 K, respectively. Because of the 29-K SC originating from the coupling of both B−2p and Ce−5d orbital states with several soft phonon modes induced by Fermi surface nesting and Kohn anomalies—fundamentally different from that in isostructural MgB2, WB2, and α−MoB2—CeB2 thus can be classified as another high-Tc superconductor.

Source-reported materials — not catalogue approval

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