Session: 10-01 Interactive Presentations

Paper Number: 100324

100324 - Magnesium Doping Enhances Thermal Conductivity of Polymerized Fullerene Crystals 

Impurity and defect atoms are known to significantly lower the thermal conductivity of crystalline solids due to the scattering of heat-carrying vibrations (phonons), even at small concentrations. This impurity scattering influences higher frequency vibrations more-so than lower frequencies. Recently, polymerized fullerene crystals have been synthesized with the intercalation of alkali earth metals, such as magnesium, thereby offering tunable control over their thermal and physical properties through the replacement of weak van der Waals interactions between individual molecules with strong covalent bonds. In this work, we conduct molecular dynamics simulations to uncover the drastic enhancement of thermal conductivity along the plane of covalently bonded fullerenes, as well as the effect of metal intercalation on the thermal conductivity. These simulations show an increase of 35 times the thermal conductivity of bulk, FCC phase fullerene, owing to the introduction of covalent bonds between fullerene molecules. Moreover, we find that this thermal conductivity is highly anisotropic based on the bonding orientation of the covalent bonds between fullerene molecules. The addition of magnesium atoms into the structure reduces this anisotropy through impurity scattering. Interestingly, we find that the thermal conductivity of the metal intercalated structure is comparable to or higher than that of the pristine polymerized fullerene structure at room temperature, counterintuitive to the idea of impurity scattering. This is attributed to the competing effects of anharmonic phonon-phonon (Umklapp) scattering, which dominates the reduction in thermal conductivity for the pristine structure at higher temperatures, and impurity scattering, which does not show a temperature dependence like Umklapp processes. As these polymerized fullerene materials have the potential to be used as battery electrode materials, these findings suggest that the metal intercalation into polymerized fullerene during cycling improves the heat transfer properties of these materials at room temperature, potentially offering better thermal management of battery systems.

Presenting Author: Jaymes Dionne University of Rhode Island