Prediction of thermodynamically stable Li–B compounds at ambient pressure

Abstract

To clarify controversial structures and phase stability in the Li–B system, we predicted energetically favorable compounds and crystal structures of the Li–B binary system at ambient pressure, mainly including Li₆B₅, LiB₂, and LiB₃, from ab initio evolutionary structure simulations and further investigated physical properties of stable Li–B compounds using first-principles methods. Metallic Li₆B₅, predicted in our simulations, has trigonal symmetry with space group R32 and contains linear B chains, but its superconducting T_c is low according to the electron–phonon coupling calculations. Orthorhombic LiB₂ (Pnma) and tetragonal LiB₃ (P4/mbm) are zero-gap semiconductors; LiB₂ is a Dirac semimetal, and both LiB₂ and LiB₃ are promising thermoelectric materials.