Thermal Conductivity of Hydrous Wadsleyite Determined by Non-Equilibrium Molecular Dynamics Based on Machine Learning

D Wang and ZQ Wu and X Deng, GEOPHYSICAL RESEARCH LETTERS, 49, e2022GL100337 (2022).

DOI: 10.1029/2022GL100337

The thermal conductivity of minerals is a fundamental parameter in understanding the evolution and dynamics of the Earth. Wadsleyite, the major mineral in the mantle transition zone (MTZ), can contain abundant water. However, how water affects its thermal conductivity remains unknown. Here, we predicted the thermal conductivity of dry and hydrous wadsleyite at high pressure and temperature (P-T) by combining non- equilibrium molecular dynamics and machine learning potential trained with data from first-principles calculations. We found that the thermal conductivity of wadsleyite is anisotropic and is reduced by similar to 10% in the P-T conditions of the MTZ by the presence of 0.81 wt.% water. The heat flow toward the slab tends to follow the direction with the lowest thermal conductivity due to the lattice-preferred orientation of wadsleyite and olivine. Both hydration and thermal-conductivity anisotropy slow down the heating of slabs, allowing hydrous minerals and metastable olivine to survive in the deeper mantle.

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