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 (κL) of highly anharmonic crystals have long been challenging in condensed matter and materials physics. With recent theoretical advances, the calculation of κL 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 κL of Tl3VSe4 and make a rigorous comparison of κL 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 κL, 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 κL owing to the mixing of higher-order IFCs into the lower-order IFCs. Our work discloses the potential uncertainties of κL that arise from the choice of different flavors of IFCs and underscores the pressing need for more rigorous and robust approaches to extracting IFCs.