Thermal Kharkiv Seminars: "Heat Capacity and Thermal Conductivity of Solids at Low Temperatures"
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Energy Transport in Superionic Crystals
Prof. Yanguang Zhou
Hong Kong University of Science and Technology
Compared with conventional solids such as crystalline silicon, the molecular structure of superionic crystals is special. The anions form a rigid sublattice while cations are highly disordered and superionic with liquid-like mobilities, which makes the transport property of superionic crystals nontrivial and forms a judicious platform to study unique energy exchange mechanism between the rigid sublattice and an ion-conducting subsystem. For example, researchers found that more than 87% of Li+ ion diffusion in the superionic Li3.042Ge0.042P0.958O4 originates from less than 10% of the vibrations between 8 and 20 THz. For another example, our recent preliminary results indicate that thermal conductivity resulting from the diffusion of liquid-like cations in superionic Li2S can contribute around ~30% of the total thermal conductivity, suggesting that thermal transport channels resulting from lattice vibrations and the diffusion of liquid-like cations should be considered. These unusual transport properties, which are strongly related to interactions between ions and vibrations in superionic crystals, however, have rarely been investigated. This is mainly because the conventional theory fails to treat systems with significant movement of ions.
In this talk, I will introduce our developed methodology to quantify the detailed transport process in superionic crystals, and unveil the understanding mechanisms for the abnormal transport phenomena observed in superionic crystals.
[1] Y. Xu, X. Xiang, Z. Li, Q. Zheng, Y. Yu, Y. Zhou, Local Ionic Enthalpy Mismatch as the Origin of High Thermoelectric Performance in Superionic Crystals, Phys. Rev. B 114, 045201, (2026)
[2] Y. Xu, X. Xiang, Z. Li, Y. Lu, Y. Zhou, Fast Ionic Transport Governed by Collective Vibrational Dynamics, Phys. Rev. Lett. 136, 126302, (2026)
[3] W. Liu and Y. Zhou, Energy Transport in Superionic Crystals, Phys. Rev. Lett.134b>, 146301 (2025).
[4] Y. Xu, H. Fan and Y. Zhou, Quantifying Spectral Thermal Transport Properties in Framework of Molecular Dynamics Simulations: A Comprehensive Review, Rare Met. 42, 3914 (2023).
[5] Y. Zhou and S. Volz, Thermal Transfer in Amorphous Superionic Li2S, Phys. Rev. B 103, 224204 (2021).
[6] Y. Zhou, S. Xiong, X. Zhang, S. Volz and M. Hu, Thermal Transport Crossover from Crystalline to Partial-crystalline Partial-liquid State, Nat. Commun. 9, 4712 (2018).
[7] B. Wu, Y. Zhou and M. Hu, Two-Channel Thermal Transport in Ordered-Disordered Superionic Ag2Te and Its Traditionally Contradictory Enhancement by Nanotwin Boundary, J. Phys. Chem. Lett. 9, 5704 (2018).
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