Atomic structural disorder—such as defects, dislocations, and grain boundaries—strongly affects how heat flows through network solids used in energy technologies, including nanoporous carbon electrodes and graphite moderators for nuclear reactors. Yet existing models of heat transport in disordered solids cannot fully explain how atomic structure relates to macroscopic conductivity in materials that are neither fully crystalline nor glassy. We address this long-standing challenge by developing a new framework that directly links the degree of atomic disorder to the thermal conductivity of complex network solids.
To quantify disorder, we introduce a measure called bond-network entropy, which counts the number of distinct local atomic arrangements within a material’s bond network. Using this descriptor together with the Wigner heat-transport equation, we establish fundamental relations between atomic-level disorder, patterns of atomic vibrations, and the distances over which these vibrations relax. This combined approach allows us to extend the classic “phonon liquid” concept, originally proposed by Charles Kittel in 1949, to describe how length scales of structural disorder affect the material’s ability to conduct heat.
Our results provide a fundamental understanding of how structural disorder governs thermal transport in energy materials; this has direct applications to the design of materials for nuclear reactors, as it exposes the relationship between their heat-management performance and their structural degradation caused by neutron irradiation. This new perspective also offers practical guidance for designing materials with tailored heat conduction—such as carbon electrodes for supercapacitors or thermal insulators—by precisely tuning their internal atomic structures.
Press release: https://quantum.columbia.edu/news/columbia-scientists-explain-how-atomic-disorder-controls-heat
Open-access article: https://journals.aps.org/prx/abstract/10.1103/w4p6-b9mp
