First-principles investigations of the physical properties of lithium niobate and lithium tantalate

The crystal, electronic structural, elastic and the thermodynamic properties of LiNbO3 and LiTaO3 are investigated by using the first-principles plane-wave pseudopotential density function theory within the generalized gradient approximation (GGA) or local density approximation (LDA). The calculated equilibrium lattice parameters, elastic properties and the bulk modulus for LiNbO3 and LiTaO3 are in good agreement with the available experimental data. Furthermore, the static dielectric constant, optical permittivity and effective mass are reported. Finally, the thermodynamic properties of LiNbO3 and LiTaO3 such as the free energy, entropy, enthalpy, heat capacity and Debye temperature are given for reference.