Prediction of thermodynamically stable Li-B compounds at ambient pressure

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.