First-principles calculations of vibrational and thermodynamical properties of rare-earth diborides

We have tried to theoretically predict the lattice dynamical and thermodynamic properties of rare earth diborides (XB2, X = Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm) in AlB2-type structure based on density functional theory within generalized gradient approximation. The calculated equilibrium lattice parameters are in overall agreement with the available experiment and other theoretical results. The phonon dispersion curves are derived by using the direct method. The lattice dynamical results are showed that these compounds are dynamically stable for the considered structure, and these properties exhibits, almost, similar trend for these compounds. In addition, thermodynamic properties such as the free energy, enthalpy, entropy and heat capacity are, also successfully predicted and analyzed with the help of phonon dispersion.