First-principles phonon calculations for lattice dynamics, thermal expansion and lattice thermal conductivity of CoSi at high temperature region

Abstract

This study presents the first-principles phonon calculations to understand the experimental thermal expansion ($\alpha (T)$) and lattice thermal conductivity (${\kappa }_L$) of CoSi at high temperature region. Phonon dispersion is computed using finite displacement method and supercell approach by taking the equilibrium crystal structures obtained from DFT. The calculation of $\alpha (T)$ is done under quasi-harmonic approximation. The ${\kappa }_L$ is calculated using first-principle anharmonic lattice dynamics calculations under single-mode relaxation time approximation. Calculated $\alpha (T)$ in the temperature range $0-1300$ K gives the good match with existing experimental data. The calculated value of ${\kappa }_L$ ($\sim$8.0 W/m-K) at 300 K is found to be in good agreement with the experimental value of $\sim$8.3 W/m-K. The temperature dependent of phonon lifetime due to phonon-phonon interaction is calculated to understand the behaviour of ${\kappa }_L$. Present study suggests that ground state phonon dispersion obtained from DFT based methods gives reasonably good explanation of experimental $\alpha (T)$ and ${\kappa }_L$.

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