Theoretical investigations of physical stability, electronic properties and hardness of transition-metal tungsten borides WBx(x=2.5, 3)

Using pseudopotential plane-waves method, we calculated the elastic properties, electronic properties and hardness for hexagonal P6(3)/mmc-2u W2B5 and R-3m-6u WB3. The elastic properties were derived to discuss the stability and bonding composition. It is observed that ionic, metallic bonding and covalent component coexist in these two compounds. Then, the electronic properties were carried out to discuss their conductivity, chemical bonding components and orbital hybridization. What is more, we employed a semiempirical method considering the role of metallic components to evaluate the hardness of these two crystals. Mechanical properties and large hardness of them indicate that they are hard materials. (C) 2015 Elsevier B.V. All rights reserved.