First-principles calculation of the structural and elastic properties of ternary metal nitrides Ta_xMo_1-xN and Ta_xW_1-xN

Abstract

View the article online for updates and enhancements. Related contentRelationships between composition and properties of (Cr/Ti)SiN and (Cr/Ti)CN alloys: anab initio study J Houska, J E Klemberg-Sapieha and L Martinu -Ab initio investigations of the strontium gallium nitride ternaries Sr3GaN3 and Sr6GaN5: promising materials for optoelectronic Souraya Goumri-Said, Haci Ozisik, Engin Deligoz et al. Abstract: First-principles pseudo-potentials calculations of the mixing enthalpy, of the lattice constants a 0 and of the single-crystal elastic constants c ij for ternary metal nitrides Ta x Me 1-x N (Me=Mo or W) alloys considering the cubic B1-rocksalt structure is carried out. For disordered ternary alloys, we employ the virtual crystal approximation VCA in which the alloy pseudopotentials are constructed within a first-principles VCA scheme. The supercell method SC is also used for ordered structures in order to evaluate clustering effects. We find that the mixing enthalpy still remains negative for Ta x Me 1-x N alloys in the whole composition range which implies these cubic Ta x Mo 1-x N and Ta x W 1-x N ordered solid solutions are stable. We investigate the effect of Mo and W alloying on the trend of the mechanical properties of TaN. The effective shear elastic constant c 44 , the Cauchy pressure (c 12 -c 44 ), and the shear to bulk modulus G/B ratio are used to discuss, respectively, the mechanical stability of the ternary structure and the brittle/ductile behavior in reference to TaN, MeN alloys. We determine the onset transition from the unstable structure to the stable one B1-rocksalt from the elastic stability criteria when alloying MeN with Ta. In a second stage, in the frame of anisotropic elasticity, we estimate by one homogenization method the averaged constants <C ij > of the polycrystalline Ta x Me 1-x N alloys considering the special case of an isotropic medium with no crystallographic texture.