Thermal transport properties of lowermost mantle minerals - Insights from atomic-scale simulations

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Heat flow through the core-mantle boundary (CMB) is one of the central processes associated with the generation of the geomagnetic field and the temporal evolution of the Earth’s core. The amount of heat transferred is determined by the thermal transport properties of the respective materials, which have been insufficiently constrained at CMB conditions. In this project, we will use atomic-scale numerical simulations to predict the thermal conductivity of the materials in the Earth’s lowermost mantle. In the first funding period of the DeepDyn Priority Program, the focus is on the lattice thermal conductivity of (Mg,Fe)O ferropericlase, Fe- and Al-bearing MgSiO3 bridgmanite and post-bridgmanite, and CaSiO3 perovskite. The main research objectives are (1) to quantify the reduction of thermal conductivity due to the effect of mass disorder in the solid solutions at lower mantle conditions and (2) to better understand and reduce the uncertainties arising from the specific numerical algorithm used to derive the thermal conductivity and from the atomic interaction potential used in the simulations. Different atomic-scale simulation methods, such as equilibrium and non-equilibrium molecular dynamics simulations or the Boltzmann transport equation approach, are systematically benchmarked for materials and thermodynamic conditions of interest here. Parameterization of polarizable ionic interaction potentials provides an additional method for modeling solid solutions. These new potentials are expected to make more realistic predictions than existing force fields. At the same time, they are much more efficient than computationally intensive ab initio simulations, which have so far been applied almost exclusively for Mg end-members and serve here mainly as a reference for the new potentials. The results of the simulations will be further used to parameterize the thermal conductivity of the lower mantle minerals as a function of pressure, temperature, and chemical composition, and to develop an improved model of heat flow through the CMB.