Thermal and Electrical Conductivity of Iron at Planetary Core Conditions from Ab Initio Computations

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The thermal and electrical conductivities of iron at high pressure and temperature are key constraints in determining the character of magnetic field generation in, and thermal history of, terrestrial planetary cores. Yet, as a result of tremendous technical challenges associated with the measurement of these properties at high pressure, their values remain very uncertain, varying by about a factor of three. As an example, this difference is sufficient to result in notably different thermal histories for the Earth s core, which crucially determines the development and generation of its magnetic field. We will accurately and reliably compute the thermal and electrical conductivity of the fcc, bcc, hcp, and liquid iron, over the range of pressures and temperatures relevant to terrestrial cores (0-400 GPa; 1000-7000 K). To do this we will use state of the art electronic structure methods in the framework of density-functional theory (DFT), to independently obtain the lattice thermal conductivity, electronic thermal conductivity and electrical conductivity. This will also enable us to self-consistently test, at high pressure and temperature, the theoretical approximations upon which current estimates of electrical and thermal conductivity at very high pressures are based.