Ab initio study of the electronic, optical and thermodynamic properties of the ternary phosphides LiAeP (Ae = Sr, Ba)

We report the results of an ab initio study of the electronic, optical and thermodynamic properties of the LiBaP and LiSrP compounds using the pseudopotential plane-wave method within the framework of the density functional theory with the GGA-PBEsol. The calculated equilibrium structural parameters are in good agreement with the available experimental data. The energy band dispersions along the high symmetry directions in the k-space and the density of states diagrams are computed and analyzed. The obtained energy bands show that both examined crystals are indirect band gap semiconductors. The chemical bonding character is examined via electron density map plots. The optical properties are predicted for an incident radiation in an energy range up to 15 eV, and the origins of the main peaks in the optical spectra are discussed in terms of the calculated electronic band structure. We have also predicted the temperature and pressure dependencies of the unit-cell volume, thermal expansion coefficient, heat capacity, Debye temperature and Grüneisen parameter.