Accurately Predicting the Thermal Conductivity of Two-Dimensional Pentagonal Palladium Ditelluride: A Critical Revisit

Most experimentally studied two-dimensional (2D) materials to date are composed of hexagonal building blocks. Palladium ditelluride (PdTe₂), a member of layered transition metal dichalcogenides (TMDCs), has aroused considerable research interest due to the coexistence of superconductivity and type-II Dirac Fermions. Motivated by the recent successful fabrication of the pentagonal PdTe₂ monolayer (p-PdTe₂), we investigated its thermal transport properties using ab initio calculations combined with the Boltzmann transport equation (BTE). Notably, by employing the temperature-dependent effective potential method to compute the interatomic force constants, we successfully eliminated the imaginary phonon frequencies of the out-of-plane acoustic phonon modes (flexural mode, ZA) and corrected its dispersion from an unphysical linear behavior to a physically quadratic form (ω ∼ q²) near the Γ point in the first Brillouin Zone of monolayer p-PdTe₂. We further predicted anisotropic room-temperature phonon thermal conductivities (κ_p) of 55.32 and 25.62 W/mK along the principal in-plane directions. Our results show that the ZA modes dominate κ_p, owing to their long relaxation times, which arise from the scattering selection rule that forbids three-phonon processes involving an odd number of ZA modes in 2D materials. We further find that the ZA modes exhibit strong anharmonicity arising from the combined effects of weak Pd–Te bonding, pronounced bond-strength disparity, and intrinsically low crystal symmetry. Our results offer a comprehensive understanding of thermal transport in p-PdTe₂ monolayers and may aid in the design of PdTe₂-based devices, giving opportunities to explore applications such as multifunctional nanoelectronics.