Vibrational properties of Re2N and Re3N compounds

Using first-principles calculations, we have studied the structural, lattice dynamical and thermodynamical properties of the recently synthesized Re₂N and Re₃N compounds. The generalized gradient approximation is used to model exchange-correlation effects. The phonon dispersion curves are derived using the direct method. The calculated equilibrium lattice parameters are in overall agreement with the available experimental and theoretical results. The present phonon dispersion results show that both compounds are dynamically stable for the structures considered. The temperature-dependent behavior of thermodynamical properties, such as free energy, entropy, heat capacity, and internal energy, is also presented.