Atomic bonding in the AlLiB14

•Identifies charges in AlLiB14.•Identifies electronic structure of AlLIB14 including.•Identifies bonding/antibonding nature of electronic states.•Examines impact of strain on electronic states.

The underlying nature of atomic bonds in the orthorhombic AlLiB14 crystal is studied using first-principles methods. Significant charge transfer is observed upon bonding, which is responsible to maintain good mechanical strength of the crystal. Individual bonding or anti-bonding states are identified which explains the correlation between the optimal mechanical strength and the electronic occupation of individual atomic orbitals. When the Fermi level is 0.35 eV inside the valence band the crystal has its maximum strength, which is the nominal position of the Fermi level in the experimentally-observed, off-stoichometric orthorhombic borides. These results indicate that the soft-phonon modes previously identified in the literature allow the crystal to reach the optimal stability. Due to the unique crystallographic symmetry, the impact of uniaxial compressive strain on the individual bonds is also examined in the end.

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