First-principles investigation of the structural, mechanical and electronic properties of the NbO-structured 3d, 4d and 5d transition metal nitrides

We performed ab initio calculations on 29 transition metal nitrides from the 3d, 4d and 5d rows, in NbO structure. We calculated cohesive energy, lattice constant and elastic constants C$_{\mathrm{11}}$, C$_{\mathrm{12}}$ and C$_{\mathrm{44}}$, and derived mechanical moduli, related ratios and hardness. For five of the ten 3d transition metal nitrides, cohesive energy in this new structure is similar to that of the same composition in the rocksalt structure. The lattice constant and bulk modulus were found to be anti-correlated. We observed the correlation between the shear modulus (G), Pugh's ratio (k) and derived Vickers hardness (H$_{\mathrm{V}})$. The nitrides, CrN, MoN and WN in NbO structure show values of H$_{\mathrm{V}}$ larger than 20 GPa. We showed systematically that C$_{\mathrm{44}}$, G, k and H$_{\mathrm{V}}$ are anti-correlated with the number of electronic states around E$_{\mathrm{F}}$. The local density of states demonstrating systematic evolution of the electronic structure was studied. Bader charge transfer analysis was performed. This work has been published as Liu et al., Comput. Mater. Sci. 84, 365 (2014).