Theoretical Investigation on the Elastic Properties, Bond Stiffness and Hardness of WX2 (X = B and N)

Abstract

In this paper, we investigate the elastic properties, bond stiffness, hardness and Debye temperatures for hexagonal P6₃/mmc WX₂ (X = B or N). It is observed that these two compounds are stable in mechanics. Both these two have three typical bonds, W-X bonds, X-X and W-W bonds. By investigating the bond stiffness of these three types of bonds, we found that the bulk modulus of WX₂ is mainly determined by W-X and W-W bonds, while the shear modulus is mainly determined by X-X bonds. In addition, using a theoretical model, we evaluate the hardness of these two compounds. Results showed that the Vickers hardness of WN₂ is much lower than that of WB₂. What’s more, by calculating the Debye temperatures, we found the melting point of WN₂ is much lower than WB₂, and the overall chemical bonds in WB₂ are stronger than that of WN₂.