Atomistic Thermal Transport in Disordered Materials

We have developed a technique to spatially decompose thermal conductivity onto atomic sites. We call this method site-projected thermal conductivity [C. Ugwumadu et al.,PSS-B, 2500316, 2025]. The method is based on the Green-Kubo formula and the work of Allen [P. B. Allen and J. L. Feldman, Phys. Rev. B 48, 12581, 1993] on thermal conductivity in disordered materials.

We demonstrate the utility of the method by applying it to various disordered systems, such as amorphous graphene, amorphous silicon, and amorphous Ge₂Se₂Te₅. The results correlate the topological and chemical disorder with the thermal defects. In amorphous graphene, heat transport is observed to prefer six-membered carbon rings.  In amorphous silicon, filamentary structures are found to dominate the heat conduction. We quantify the contribution of different phonon modes to total thermal conductivity. In amorphous Ge₂Se₂Te₅, the heat transport is dominated by filamentary structures within the network with higher Te concentration. We directly compute heat transport from molecular dynamics and show that the results are consistent with our method.