Effect of the A‑Site\nCation on the Lattice\nThermal Conductivity of Nitride Perovskites

In this report, the effect of A-site cations on the lattice\nthermal\nconductivity (κ<sub>L</sub>) of nitride perovskites was comparatively\nstudied by first-principles calculations in similar crystal structures,\nLaWN<sub>3</sub> and YWN<sub>3</sub>. The A-site cation is found to\ninduce notable differences in acoustic (0–125 cm<sup>–1</sup>) and low-lying optical phonons (125–500 cm<sup>–1</sup>), which translate into a large κ<sub>L</sub> discrepancy (around\n20%). It is worth mentioning that the higher κ<sub>L</sub> of\nLaWN<sub>3</sub> is contributed mostly by atom N in the [WN<sub>6</sub>] octahedron, although the average W–N bond length is almost\nidentical for LaWN<sub>3</sub> and YWN<sub>3</sub>. Faster group velocity,\nlonger lifetime, and larger Grüneisen parameters in optical\nbranches are observed in LaWN<sub>3</sub>, which should be ascribed\nto the longer distance between the cation La and the [WN<sub>6</sub>] octahedron. Our findings provide a deep understanding of the role\nof the A-site cation in the thermal conductivity of nitride perovskites.