The effect of Mo atoms in ternary nitrides with eta-type structure

The effect of Mo atoms in ternary eta-type nitrides, T(3)Mo(3)N and T(2)Mo(4)N (T = Fe, Co, Ni), has been investigated by atomistic simulation. The calculated lattice constants and atomic coordinates are in good agreement with experiments. Calculated results show that adding more Mo atoms makes the crystal energies of T(2)Mo(4)N decrease markedly, which indicates that Mo atoms can stabilize these nitrides. The Mo atoms prefer to occupy the 16d sites and avoid the 32e sites in T(2)Mo(4)N. The calculated elastic constants and bulk modulus are compared with the experimental and the density functional theory (DFT) results. Furthermore, in order to evaluate the thermodynamic contribution by Mo atoms, the phonon density of states, specific heat, and vibrational entropy of Fe(3)Mo(3)N and Fe(2)Mo(4)N are also investigated. (C) 2008 Elsevier Ltd. All rights reserved.