Structural properties, electronic structures and optical properties of WB2 with different structures: A theoretical investigation

The structural, electronic and optical properties of six WB2 diborides with hP3, hP6, hP12, oP6, hR9 and hR18 structures were systematically investigated using the first-principles calculation based on density functional theory. The optimized atomic coordinates and lattice parameters agree well with the corresponding experimental and theoretical results. All WB2 are energetically stable, and hP6-WB2 has the best phase stability and hP3-WB2 shows the worst phase stability. The results of density of states and the charge density differences indicate that WB2 have the strong W-B and B-B covalent bonds. The hardness was obtained from the Mulliken population. The predicted values of absorption coefficient α(ω) and reflectivity R(ω) reveal that the laser with a longer wavelength is recommended during the synthesis of WB2 coatings on the substrate surface using the Nd-YAG laser. Finally, the anisotropy in optical properties for WB2 was discussed via the polycrystalline and directional static dielectric constants ε1(0) and static refractive indexes n(0).