Structural stability and mechanical property of WN from first-principles calculations

The structure and mechanical stability of WN crystal are investigated using the first-principle calculations based on density functional theory (DFT). Eight possible crystal structures are studied and the results reveal that WC-type WN is metastable, which is different from the conclusions obtained by Schoenberg. Our calculated results show that NiAs-type WN is not only the most energy favorable but also meets the requirements of mechanical stability. The investigation on anisotropic incompressibility indicates that NiAs-type WN is an ultra-incompressible material, especially in c-axis direction, which is much more incompressible than that of diamond. Calculated density of states, charge density distribution as well as Mulliken population analysis show that the chemical bonding of WN is a mixture of covalent, ionic and metallic bonding. (C) 2009 Elsevier B.V. All rights reserved.