Pressure-regulated rotational guests in nano-confined spaces suppress heat transport in methane hydrates
Chengyang Yuan, Hongxiang Zong, Hongsheng Dong, Lei Yang, Yufei Gao, Zhen Fan, Lunxiang Zhang, Jiafei Zhao, Yongchen Song, John S. Tse
Abstract
Materials with low lattice thermal conductivity are essential for various heat-related applications like thermoelectrics, and usual approaches for achieving this rely on specific crystalline structures. Here, we report a strategy for thermal conductivity reduction and regulation via guest rotational dynamics and their couplings with lattice vibrations. By applying pressure to manipulate rotational states, we find the intensified rotor-lattice couplings of compressed methane hydrate MH-III can trigger strong phonon scatterings and phonon localizations, enabling an almost three-fold suppression of thermal conductivity. Besides, the disorder in methane rotational dynamics results in anharmonic interactions and nonlinear pressure-dependent heat transport. The overall guest rotational dynamics and heat conduction changes can be flexibly regulated by the rotor-lattice coupling strength. We further underscore that this reduction mechanism can be extended to a wide range of systems with different structures. The results demonstrate a potentially universal method for reducing or controlling heat transport by developing a hybrid system with tailored molecular rotors. Molecular disorder plays an important role in the thermal conductivity of materials. Using atomistic simulations, the authors show that thermal conductivity can be pressure-regulated in methane hydrates by manipulating disordered guest rotational dynamics.