ThN’s Lattice-Assisted Thermal Conductivity Revisited

The calculated electron density of states of ThN at the Fermi energy is low, which is in agreement with a very low electronic heat capacity coefficient measured experimentally. Therefore, it has been claimed that the electronic thermal conductivity of ThN should be low. However, the total thermal conductivity as measured recently is high. We used Quantum Espresso and EPW codes based on density-functional theory to evaluate the electron density of states, the electronic heat capacity coefficient, and electronic heat conductivity. We confirmed that the calculated electronic heat capacity coefficient was low due to the evaluated low electron density of states of ThN at the Fermi energy while the calculated electronic thermal conductivity of ThN was found to be high. However, the method of evaluating the remaining contribution from phonons is still disputed. The calculated lattice thermal conductivity of ThN is over-predicted unless a large smearing is applied in phono3py code. ShengBTE calculations predict that the lattice thermal conductivity of a pure single crystal may be one order of magnitude higher than the currently measured relatively low conductivity (~20 Wm−1K−1) at room temperature.