Lattice thermal conductivity for complex 2D materials, an ab initio approach

For a material to be suitable for thermoelectric applications, it must have a low lattice thermal conductivity (𝜿_latt), as this can greatly enhance the figure of merit (zT). In this study, we conducted a comprehensive computational analysis of the lattice thermal conductivity of three materials: WSe₂, WSSe, and Sn₂SSe. These materials have different levels of complexity. WSe₂ is a known transition metal dichalcogenide (TMD), while WSSe and Sn₂SSe are Janus materials due to their asymmetry along the z-axis. We performed this analysis using density functional theory (DFT) and density functional perturbation theory (DFPT) methodologies together with semi-classical Boltzmann transport theory. We obtained values close to 50 W/(m·K) for WSe₂, which aligns well with prior calculations. Furthermore, we obtained low lattice thermal conductivity values of 4.7 and 2.7 W/(m·K) for WSSe and Sn₂SSe, respectively. These low values suggest that these two materials have good potential for use in thermoelectric devices.