The crystal structures, phase stabilities, electronic structures and bonding features of iridium borides from first-principles calculations.

We present results of an unbiased structure search for the lowest energy crystalline structures of various stoichiometric iridium borides, using first-principles calculations combined with particle swarm optimization algorithms. As a result, besides three stable phases of 2/-IrB, 2-IrB, and -IrB, three promising metastable phases, namely, 2/-IrB, 2/-IrB, and -IrB, whose energies are within 20 meV per atom above the convex hull curve, are also identified at ambient pressure. The high bulk modulus of 301 GPa, highest shear modulus of 148 GPa, and smallest Poisson's ratio of 0.