DFT calculation of thermo-elastic properties and phonon dispersions for Terbium monopnictides TbN and TbP in rock salt structure

Abstract

The full potential all electron linearized augmented plane wave (FP- LAPW) method, as implemented in the suite of software WIEN2K, were performed to study the structural, electronic, magnetic, mechanical, dynamical and thermodynamic properties of Terbium monopnictides TbN and TbP. The exchange correlation interaction was treated within the generalized gradient approximation (GGA-PBE) and GGA-PBE + U scheme. We found that the NaCl phase is the lowest energy phase as a function of the volume. The calculated lattice parameters are in good agreement with experimental and other theoretical values. The elastic properties of the studied compounds are only investigated in the most stable calculated phase.From the elastic parameter, it is inferred that these compounds are elastically stable and brittle in nature. The phonon dispersion curves for both compounds are also computed in the NaCl (B1) structure, we found that TbN and TbP are dynamically stable in NaCl phase. The band structure and corresponding density of states have also been determined and analyzed using GGA-PBE, GGA-PBE + U and mBJ-GGA-PBE approaches.Furthermore, we have analyzed the thermodynamic properties such as the heat capacities, entropy, and free energy have been calculated by using the phonon frequencies. Also, the Debye temperatures of TbN and TbP are calculated to be 491 K and 348 K, respectively. This study will be helpful for future device applications such as advanced thermoelectric applications.