Manipulating elastic and mechanical properties of Cu3N through site selective Ag doping: First principles investigation

Abstract

In the present work, structural, elastic and mechanical properties of pure and Ag doped Cu3N systems are investigated using density functional calculations. The doped atom is incorporated into the host lattice by filling the vacant interstitial site (interstitial doping) or substituting Cu (substitutional doping). From the calculated elastic constants, the pure and both kinds of doped systems are qualified as mechanically stable compounds. Modifications of the elastic and mechanical properties of Cu3N due to the interstitial and substitutional Ag doping are systematically predicted by analyzing the estimated elastic moduli (Young’s, bulk and shear moduli, and Poisson’s ratio), Pugh’s constant and Vicker’s hardness. The results predict, interstitial (substitutional) doping of Ag strengthens (weakens) mechanical stability of the parent compound. Further, elastic anisotropy of these systems is examined by estimating various anisotropy factors and mapping spatial variation of the elastic moduli. The anisotropy of elastic properties of Cu3N is greatly reduced when Ag is doped at the interstitial site. On the other hand, substitutional Ag doping magnifies the elastic anisotropy. Finally, velocity of acoustic waves is estimated from the elastic constants and its anisotropy is examined. It is verified that, both kinds of Ag doping reduce the average acoustic velocity.