A Unified Theory of Thermal Conductivity of Liquids and Amorphous Solids

The thermal transport mechanisms in both liquids and amorphous solids remain unclear due to the lack of successful theories. Several models have been proposed to explain the thermal conductivity, for example, the Bridgman's model for liquids with simple molecules, the minimum thermal conductivity model for amorphous solids, and the thermal resistance network model for polymers. In this paper, we propose a unified theory to calculate the thermal conductivity of liquids, organic and inorganic amorphous solids simultaneously. The atomic/molecular arrangement of liquids and amorphous solids is considered by including the coordination number of touching neighbours. The theoretical calculations are in excellent agreement with the experimental data without using any fitting parameters. The chemical structure effect on thermal conductivity can be included in our model. All above three existing models are proved to be special cases of our theory. We find that the unification of thermal transport in liquids and amorphous solids originates from the similar atomic/molecular structures which possess short-range order but no long-range order.