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arXiv · 1904.12038

Phonon Lifetimes and Thermal Conductivity of the Molecular Crystal ${\alpha}$-RDX

Gaurav Kumar·Francis G. VanGessel·Daniel C. Elton·Peter W. Chung
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Abstract

The heat transfer properties of the organic molecular crystal ${\alpha}$-RDX were studied using three phonon-based thermal conductivity models. It was found that the widely used Peierls-Boltzmann model for thermal transport in crystalline materials breaks down for ${\alpha}$-RDX. We show this breakdown is due to a large degree of anharmonicity that leads to a dominance of diffusive-like carriers. Despite being developed for disordered systems, the Allen-Feldman theory for thermal conductivity actually gives the best description of thermal transport. This is likely because diffusive carriers contribute to over 95% of the thermal conductivity in ${\alpha}$-RDX. The dominance of diffusive carriers is larger than previously observed in other fully ordered crystalline systems. These results indicate than van-der Waals bonded organic crystalline solids conduct heat in a manner more akin to amorphous materials than simple atomic crystals.

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Gaurav Kumar, Francis G. VanGessel, Daniel C. Elton, Peter W. Chung. 2019-04-26. Phonon Lifetimes and Thermal Conductivity of the Molecular Crystal ${\alpha}$-RDX. https://doi.org/10.1557/adv.2019.278

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