First-principles study of the stability, electronic and mechanical properties of Cr2N and CrN with the variation of Ni doping concentration

Abstract

First-principles approach was applied to investigate the stability, electronic and mechanical properties of Cr2-xNixN (x = 0, 0.083, 0.167,0.250, 0.333) and Cr1-xNixN (x = 0,0.125,0.25,0.375, 0.5). The calculated formation enthalpy and mechanical stability results show that Cr2-xNixN and Cr1-xNixN are all stable. The bulk, shear and Young's modulus results indicate that different variation trend is observed in Cr2-xNixN and Cr1-xNixN with the increase of x. Base on Pugh and Pettifor criteria, Cr2N belongs to the brittle area and the ductility of Cr2-xNixN increases with the increment of x, obtain the maximum results when x = 0.333. However, CrN, which belongs to the ductile area, alloying with Ni decreases its ductility and increases its brittleness, reach the maximum brittleness when x = 0.5. The charge density difference study reveals that the doped Ni atom affects the interaction between Cr and N in Cr2-xNixN and Cr1-xNixN differently. Furthermore, the stress-strain curve of Cr2N, Cr1.833Ni0.167N, and Cr1.667Ni0.333N under shear and tensile deformation shows that the ultimate stress of Cr2N is decreased and its ductility increased. Nevertheless, the stress-strain curve of CrN, Cr0.75Ni0.25N, and Cr0.5Ni0.5N under shear and tensile deformation indicates that the strength of CrN can be enhanced and its deformation process is significantly changed when x = 0.25.