Structural, mechanical and optical properties of potentially superhard WBx polymorphs from first principles calculations

•Five WBx are compared due to structural, mechanical and optical properties.•Optical data needed for PLD of WBx thin films with Nd-YAG laser are presented.•Comparison of cohesive energies of potentially superhard WBx is shown.•None of the analyzed polymorphs have a hardness greater than 40 GPa.•The hardest one WBx polymorph, i.e. hP6-P63/mmc-WB2, reaches hardness Hv = 39 GPa.

Five potentially superhard WBx polymorphs: hP10-P63/mmc-WB4, hP16-P63/mmc-WB3, hR24-R3¯ m-WB3, hP6-P63/mmc-WB2 and oP6-Pmmn-WB2 were thoroughly analyzed within the framework of First Principles Density Functional Theory from the structural, mechanical and optical properties point of view. None of the analyzed polymorphs have a hardness greater than 40 GPa, for the hardest one hP6-P63/mmc-WB2, Hv = 39 GPa. The most stable WBx polymorph is oP6-Pmmn-WB2 with the lowest cohesive energy Ecoh = −8.299 eV/Atom. Due to our knowledge, the optical properties of WB2 and cohesive energy of tungsten borides were presented for the first time. The best optical properties for Pulsed Laser Ablation possess hP6-P63/mmc-WB2 with the lowest reflectivity 0.343 for 355 nm laser radiation.