Role of van der Waals Interactions in Modulating Thermal Transport of HfSe ₂ ‐Based Janus Superlattices

ABSTRACT The presence of van der Waals (vdW) interactions plays a crucial role in modifying phonon dispersion and scattering mechanisms, enabling a more accurate determination of lattice thermal conductivity (). In this work, we use first‐principles calculations based on density functional theory to investigate how vdW interactions influence the thermal transport properties of HfSe 2 ‐based superlattices (SL), including their Janus derivatives. Our results show that introducing a Janus layer at internal interfaces significantly changes phonon transport by promoting phonon localization and increasing phonon scattering, which reduces by nearly a factor of two compared to the bulk material. We also conduct crystal orbital Hamilton population (COHP) analysis, which reveals significant bonding heterogeneity, particularly arising from the bonding nature of Hf–Se as well as antibonding and nonbonding characteristics of Hf–Te interactions, leading to increased phonon scattering strength in Janus SL. These findings establish a fundamental framework for engineering superlattices with tailored thermal properties, offering promising avenues for thermal transport.