Combining experimental and computational approaches to determine high P and T thermal conductivity of CaGeO3 and MgSiO3 perovskite

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Knowledge of the heat transport properties of minerals at deep Earth conditions is essential for our understanding of its thermal state and evolution over geological time. Experimental measurement of lattice thermal conductivity (k) at extreme pressure (P) and temperature (T) conditions is very challenging, and computational approaches to its determination can make a significant contribution to our understanding of the thermal state of the planet. We propose to use current state of the art in atomistic simulation, first-principles molecular dynamics (FPMD), to compute k(P,T) for mantle minerals at conditions relevant to the lower mantle, by characterizing the anharmonic vibrational properties on which k depends. To test our first principles implementation of the method, we will first consider k(P,T) for MgO periclase, whereafter we will perform calculations for CaGeO3 perovskite, which we will compare to k(T) values that we will measure in situ at pressures 0 – 20 GPa. Having tested and further improved our method against these data, we will proceed to calculate k(P,T) for MgSiO3 perovskite at conditions relevant to the entire lower mantle. We will then evaluate the implications of these results for existing models of the pressure dependence of thermal conductivity, as well as the thermal evolution of Earth.