Prediction study of the elastic and thermodynamic properties of the newly discovered tetragonal SrPd2Ge2 phase

Density functional theory pseudo-potential plane-wave calculations are performed in order to predict the structural, elastic and thermodynamic properties of the newly discovered tetragonal intermetallic SrPd2Ge2. The computed equilibrium lattice constants and the internal parameter are in good agreement with the experimental findings. The effect of high pressure, up to 40 GPa, on the lattice constants shows that the contraction along the cc axis is higher than along the aa axis. The single-crystal elastic constants and related properties are calculated using the static finite strain technique. We predicted the bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio for ideal polycrystalline SrPd2Ge2 aggregates, using the Voigt–Reuss–Hill approximations. We estimated the Debye temperature and minimum thermal conductivity of SrPd2Ge2 from the average sound velocity. Through the quasi-harmonic Debye model, in which the phononic effects are considered, the temperature and pressure effects on the primitive cell volume, bulk modulus, thermal expansion coefficient, heat capacity and Debye temperature are investigated. This is the first quantitative theoretical prediction of the elastic and thermodynamic properties of the SrPd2Ge2 compound, and it still awaits experimental confirmation.

► We studied for the first time some properties of SrPd2Ge2. ► The elastic parameters increase linearly with the increasing pressure. ► Temperature and pressure effects on some macroscopic parameters are obtained.