Density functional study of thermodynamic properties, thermal expansion and lattice thermal conductivity of Fe2VAl in the high-temperature region

Here, we present the phonon calculations for thermodynamic properties, thermal expansion and lattice thermal conductivity of Fe2VAl in the temperature range of 300-800K and compare them with existing experiment. Phonon dispersion is computed using the finite displacement method and supercell approach. The positive frequencies of all the phonon modes indicate the mechanical stability of the compound. The specific heat at constant volume and Helmholtz free energy are calculated under harmonic approximation, while calculation of thermal expansion is done under quasi-harmonic approximation. Lattice thermal conductivity (kappa(L)) is calculated using first-principle anharmonic lattice dynamics calculations. The zero-point energy and Debye temperature are computed as similar to 21 kJ/mol and 638K, respectively. The calculated thermal expansions are found to be similar to 6.3 x 10(-6) K-(1) and similar to 7.2 x 10(-6) K-1 at 300 and 800K, respectively. A significant deviation between calculated (similar to 47.8W/m.K) and experimental (similar to 22.8W/m.K) values of kappa(L) are observed at 300 K. But, as the temperature increases, the calculated and experimental kappa(L) come closer with the corresponding values of similar to 17.9W/m.K and similar to 11.0W/m.K at 800K. The possible reasons for the deviation of kappa(L) are addressed. The temperature dependence of phonon lifetime is computed in order to understand the feature of kappa(L). The present study suggests that DFT-based phononic calculations provide reasonably good explanations of available experimental phonon-related properties of Fe2VAl in the high-temperature range of 300-800K. Copyright (C) 2022 EPLA