Bonding properties and superconductivity of electride Be6C under moderate pressure

Abstract

Superconducting electrides are characterized by the emergence of electrons occupying the interstitial region of lattice and exhibit coexistence of distinctive electride state and superconductivity, which have attracted wide attention. However, the underlying crucial factors governing the superconductivity and influencing the structural stability by electride states remain elusive. Here, we performed structure searches in conjunction with first-principles calculations to identify a dynamically stable electride Be6C at 40 GPa, which exhibits p-orbital type electride states and demonstrates superconductivity with a Tc of 22.4 K. Furthermore, it remains dynamically stable even down to ambient conditions while maintaining a Tc of 18.9 K. Further analyses unveiled that the dual p-hybridized electrons within the orbitals of p-orbital electride states and Be-2p mainly composed of a van Hove singularity near the Fermi level and participate in electron–phonon interaction to form Cooper pairs leading to the high-Tc. The preservation of dynamic stability for Be6C at low pressure is primarily attributed to the presence of electride states that effectively form both covalent and ionic bonding properties to bind neighbor Be cations to lower enthalpy of system and subsequently, in turn, lowering the required pressure. Our findings not only explained the underlying factors affecting superconductivity but also revealed the crucial role of electride states in determining the dynamic stability of structure, providing valuable insights for subsequent research on superconducting electrides at low pressures.