Structural and lattice dynamical properties of Zintl NaIn and NaTl compounds

► NaTl and NaIn are crystalline in B32 phase like the most of the technologically important I-III compounds. ► The structural phase transition pressures from B32 to B2 structure for NaIn and NaTl are found to be 114.2 and 43.9 GPa for NaIn and NaTl, respectively. ► Also, the lattice dynamical and the thermo dynamical properties of NaIn and NaTl in B32 phase are reported. The first-principles calculations based on the density-functional theory have been performed using both the generalized–gradient approximation (GGA) and the local-density approximation (LDA) to investigate many physical properties of NaIn and NaTl compounds. Specifically, the structural (lattice constant, bulk modulus, pressure derivative of bulk modulus, phase transition pressure ( P t )), mechanical (second-order elastic constants ( C ij ), Young’s modulus, isotropic shear modulus, Zener anisotropy factor, Poisson’s ratio, sound velocities), thermo dynamical (cohesive energy, formation enthalpy, Debye temperature), and the vibrational properties (phonon dispersion curves and one-phonon density of states) are calculated and compared with the available experimental and other theoretical data. Also, we have presented the temperature variations of various thermo dynamical properties such as free energy, internal energy, entropy and heat capacity for the same compounds.