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

This study presents the first-principles phonon calculations to understand the experimental thermal expansion ($α(T)$) and lattice thermal conductivity ($κ_{L}$) 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 $α(T)$ is done under quasi-harmonic approximation. The $κ_{L}$ is calculated using first-principle anharmonic lattice dynamics calculations under single-mode relaxation time approximation. Calculated $α(T)$ in the temperature range $0-1300$ K gives the good match with existing experimental data. The calculated value of $κ_{L}$ ($\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 $κ_{L}$. Present study suggests that ground state phonon dispersion obtained from DFT based methods gives reasonably good explanation of experimental $α(T)$ and $κ_{L}$.

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