Structural, elastic, and lattice dynamical properties of YB2 compound

In this work, density functional theory calculations on the structural, mechanical, lattice dynamical, and thermodynamical properties of YB2 in AlB2-type and monoclinic (C2/m) structures are reported. The local density approximation has been used for modeling exchange–correlation effects. We have predicted the lattice constants, bulk modulus, elastic constants, shear modulus, Young’s modulus, Poison’s ratio, Debye temperature, and sound velocities. Furthermore, the phonon dispersion curves, corresponding phonon density of states, some thermodynamical quantities such as internal energy, entropy, heat capacity, and their temperature-dependent behaviors are presented. Our structural and some other results are in agreement with the available experimental and theoretical data.

Research highlights
► The transition metal-diborides exhibit unique properties such as high-melting points, high-hardness values, and excellent oxidation resistance.
► Therefore, they are promising materials for new heat-resistant, corrosion-resistant, and wear-resistant alloys and coatings.
► The original aspects of the present calculations concern the elastic properties, mechanical results, and phonon dispersion curves, which are not considered previously, except for AlB2 structure.
► The calculated phonon dispersion curves do not contain soft modes at any direction, which confirms the stability of the AlB2 type structure, and monoclinic (C2/m) structure is dynamically unstable due to the existing of imaginary frequencies at 0 GPa.