A comprehensive first-principles analysis of phonon thermal conductivity and electron-phonon coupling in different metals

Abstract

Separating electron and phonon thermal conductivity components is imperative for understanding the principle thermal transport mechanisms in metals and highly desirable in many applications. In this work, we predict the mode-dependent electron and phonon thermal conductivities of 18 different metals at room-temperature from first-principles. Our first-principles predictions, in general, agree well with experimental data. We find that the phonon thermal conductivity is in the range of 2 - 18 $W/mK$, which accounts for 1% - 40% of the total thermal conductivity. It is also found that the phonon thermal conductivities in transition metals and transition-intermetallic-compounds (TICs) are non-negligible compared to noble metals due to their high phonon group velocities. Besides, the electron-phonon coupling effect on phonon thermal conductivity in transition metals and intermetallic compounds is stronger than that of nobles, which is attributed to the larger electron-phonon coupling constant with a high electron density of state within Fermi window and high phonon frequency. The noble metals have higher electron thermal conductivities compared to transition metals and TICs, which is mainly due to the weak electron-phonon coupling in noble metals. It is also shown that the Lorenz ratios of transition metals and transition-intermetallic-compounds hold larger deviations from the Sommerfeld value $L_0=2.44 \times 10^{-8} W ΩK^{-2}$. We also find the mean free paths (MFPs) for phonon (within 10 nm) are smaller than those of electron (5 - 25 nm). The electrical conductivity and electron thermal conductivity are strongly related to the MFPs of the electron.