Structural stability, electronic structure and mechanical properties of ZnN and CdN: A first principles study

Abstract

First principles calculations are performed to investigate the structural stability, electronic and mechanical properties of ZnN and CdN for various structures: NaCl, CsCl, zinc blende, and NiAs. The local density and generalized gradient approximations are used for exchange and correlation effects. Our calculations indicate that zinc blende (ZB) phase is the lowest energy phase for ZnN while it is the NaCl phase for CdN at normal pressure. A pressure induced structural phase transition from zinc blende to NiAs phase is predicted in ZnN, whereas NaCl to zinc blende phase and then zinc blende to NiAs phase is observed in CdN. The ground state properties like lattice parameters, bulk modulus and cohesive energy are calculated. Electronic structure reveals that both ZnN and CdN are metallic. The computed elastic constants show that these nitrides are mechanically stable in their most stable phase. The shear modulus, Young’s modulus, Poisson’s ratio and Debye temperature are also calculated. The low bulk modulus value indicates that ZnN and CdN are more compressible compared to other transition metal nitrides.