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Structural, elastic and thermodynamic properties of Ag-based oxides XAgO (X = Li and Na): An ab initio study
Allali D.1,2,∗, Amari R. 3, Boukhari A. 3, Deghfel B.4
1Physics and Chemistry of Materials Lab, Department of Physics, University of M’sila, 28000, M’sila, Algeria.
2 University of M’sila, Faculty of Technology, B.P. 166 Ichbilia, 28000, M’sila, Algeria.
Email: djamel.allali@univ-msila.dz
3Laboratory of Materials and Renewable Energy, Faculty of Sciences, Mohamed Boudiaf University of M’sila, 28000, M’sila, Algeria.
4 University of M’sila, Faculty of Science, Department of Physics, 28000, M’sila, Algeria.

Structural parameters, elastic constants and thermodynamic properties of the tetragonal ternary Ag-based oxides LiAgO and NaAgO are investigated theoretically for the first time using the plane-wave ultra-soft pseudopotential method [1] based on the density functional theory [2,3]. The optimized lattice parameters and atomic positions agree well with the available theoretical and experimental counterparts. Pressure dependence of the structural parameters is also explored. Pressure dependences of the single-crystal elastic constants Cij for LiAgO and NaAgO are explored. The elastic wave velocities propagating along the principal crystallographic directions are numerically estimated. The elastic anisotropy is estimated and further illustrated by 3D-direction-dependent of the Young’s modulus. A set of some macroscopic elastic moduli, including the bulk, Young’s and shear moduli, Poisson’s coefficient, average elastic wave velocities and Debye temperature, were calculated for polycrystalline LiAgO and NaAgO from the Cij via the Voigt-Reuss-Hill approximations [4–6]. Through the quasiharmonic Debye model [7], which takes into account the phonon effects, the temperature and pressure dependencies of the bulk modulus, unit cell volume, volume thermal expansion coefficient, Debye temperature and volume constant and pressure constant heat capacities of LiAgO and NaAgO are explored systematically in the ranges of 0–20 GPa and 0–1200 K.

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