Study of the ideal strengths, electronic and elastic properties of Mo 2 B, Mo 3 B 2 and MoB 2

Stoichiometric ratio and atomic arrangement may influence the physical properties of crystals. In this work, first-principles calculations are performed to study the ideal strengths, electronic and elastic properties of I4/m Mo2B, P4/mbm Mo3B2 and I41/amd MoB2. The dynamical, thermodynamic and mechanical stabilities of these crystals are verified. Calculated electronic properties indicate that all of them exhibit metallic character. Their bonding properties are analysed via multiple approaches. Computed elastic constants reveal that they are mechanically stable but anisotropic. The derived bulk moduli and melting temperatures suggest that they are incompressible and refractory. The stress–strain curves of representative strain patterns are calculated and the corresponding crystal deformation mechanisms are uncovered. The calculated minimum ideal strengths of Mo2B, Mo3B2 and MoB2 are 20.9, 22.9 and 16.9 GPa under the [001](110), [100](011) and [100](011) shear modes, respectively. Studies reveal that different strain modes may bring different influences on the metallicity of the crystals, and applied strains will shift the boundary between the bonding and antibonding states towards higher-energy regions. Their hardness values are also evaluated with several computational schemes. Further experiments are required to resolve the considerable discrepancies among the predicted hardness values.