First-principles calculations of lattice thermal conductivity in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Tl</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi>VSe</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>: Uncertainties from different approaches of force constants

Abstract

Accurate and reliable first-principles simulations of lattice thermal conductivity (${\ensuremath{\kappa}}_{\mathrm{L}}$) of highly anharmonic crystals have long been challenging in condensed matter and materials physics. With recent theoretical advances, the calculation of ${\ensuremath{\kappa}}_{\mathrm{L}}$ 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 ${\ensuremath{\kappa}}_{\mathrm{L}}$ of ${\mathrm{Tl}}_{3}{\mathrm{VSe}}_{4}$ and make a rigorous comparison of ${\ensuremath{\kappa}}_{\mathrm{L}}$ 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 ${\ensuremath{\kappa}}_{\mathrm{L}}$, 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 ${\ensuremath{\kappa}}_{\mathrm{L}}$ owing to the mixing of higher-order IFCs into the lower-order IFCs. Our work discloses the potential uncertainties of ${\ensuremath{\kappa}}_{\mathrm{L}}$ that arise from the choice of different flavors of IFCs and underscores the pressing need for more rigorous and robust approaches to extracting IFCs.

Topics & Concepts