Chemical ordering and temperature effects on the thermal conductivity of Ag-Au and Ag-Pd bimetallic bulk and nanocluster systems

Understanding the heat transfer mechanisms in bimetallic nanoparticles, e.g. to promote heat transfer in a nanofluid, is a significant problem for industrial and fluid mechanics related applications. Given the difficulties in interpreting experimental measurements, theoretical approaches to the prediction of thermal conductivity represent an alternative path to derive rigorous information that can guide the design of a better device for industrial applications. Molecular dynamics (MD) simulations are employed here to shed light on the thermal conductivity (TC) of silver-gold (Ag-Au) and silver-palladium (Ag-Pd) bulk systems and nanoclusters via the Green-Kubo formalism at both room and high temperatures. MD simulations are employed to investigate the thermal conductivity behavior with temperature and doping for Ag-Au and Ag-Pd nanoalloys with 256 atoms. We found that for both Ag-Au and Ag-Pd bulk alloys their thermal conductivity exhibits a non-monotonic behavior as a function of Pd and Au contents, with the predicted trends and values of TC validated by comparison with the available experimental results on bulk systems. Up to room temperature, the electronic contribution represents the main component, with a non-monotonic behavior versus Au and Pd doping, whereas at high temperature the phonon contribution becomes dominant, together with diffusion that is also shown to be a significant factor in heat transfer. In nanoalloys, we found that both the phonon and diffusion contributions to their thermal conductivity have a non-monotonic trend as a function of mole fraction.