First-principles calculations of lattice thermal conductivity in Tl3VSe4: Uncertainties from different approaches of force constants

Accurate and reliable first-principles simulations of lattice thermal conductivity (kappa L) of highly anharmonic crystals have long been challenging in condensed matter and materials physics. With recent theoretical advances, the calculation of kappa L has evolved into a sophisticated process requiring the consideration of higher levels of refinements, such as high-order phonon-phonon scattering, anharmonic phonon renormalization, and heat transport beyond the phonon gas picture. Interatomic force constants (IFCs), however, as a shared pillar of the above concepts, are sometimes ambiguously implemented in this process, resulting in non-negligible uncertainties among different studies. Here, we revisit the ultralow kappa L of Tl3VSe4 and make a rigorous comparison of kappa L obtained from IFCs extracted by different approaches (flavors). We find that the fourth-order IFCs extracted with small-displacement data (0 K) are prone to yield significant phonon frequency shifting (phonon renormalization) and four-phonon scatterings, which lead to distinctively increased or decreased kappa L, respectively. Moreover, the different flavors of second-, third-, and fourth-order IFCs extracted with the same large-displacement data (temperature-dependent) also result in significantly disparate kappa L owing to the mixing of higher-order IFCs into the lower-order IFCs. Our work discloses the potential uncertainties of kappa L that arise from the choice of different flavors of IFCs and underscores the pressing need for more rigorous and robust approaches to extracting IFCs.