Anomalous Thermal Transport across the Superionic Transition in Ice

R Qiu and QY Zeng and H Wang and DD Kang and XX Yu and JY Dai, CHINESE PHYSICS LETTERS, 40, 116301 (2023).

DOI: 10.1088/0256-307X/40/11/116301

Superionic ices with highly mobile protons within stable oxygen sub- lattices occupy an important proportion of the phase diagram of ice and widely exist in the interior of icy giants and throughout the Universe. Understanding the thermal transport in superionic ice is vital for the thermal evolution of icy planets. However, it is highly challenging due to the extreme thermodynamic conditions and dynamical nature of protons, beyond the capability of the traditional lattice dynamics and empirical potential molecular dynamics approaches. By utilizing the deep potential molecular dynamics approach, we investigate the thermal conductivity of ice-VII and superionic ice-VII '' along the isobar of P = 30 GPa. A non- monotonic trend of thermal conductivity with elevated temperature is observed. Through heat flux decomposition and trajectory-based spectra analysis, we show that the thermally activated proton diffusion in ice- VII and superionic ice-VII '' contribute significantly to heat convection, while the broadening in vibrational energy peaks and significant softening of transverse acoustic branches lead to a reduction in heat conduction. The competition between proton diffusion and phonon scattering results in anomalous thermal transport across the superionic transition in ice. This work unravels the important role of proton diffusion in the thermal transport of high-pressure ice. Our approach provides new insights into modeling the thermal transport and atomistic dynamics in superionic materials.

Return to Publications page