Reconciliation of Experiments and Theory on Transport Properties of Iron and the Geodynamo
Youjun Zhang, Mingqiang Hou, Guangtao Liu, Chengwei Zhang, Vitali B. Prakapenka, Eran Greenberg, Yingwei Fei, R. E. Cohen, Jung‐Fu Lin
Abstract
We measure the electrical resistivity of hcp iron up to $\ensuremath{\sim}170\text{ }\text{ }\mathrm{GPa}$ and $\ensuremath{\sim}3000\text{ }\text{ }\mathrm{K}$ using a four-probe van der Pauw method coupled with homogeneous flattop laser heating in a DAC, and compute its electrical and thermal conductivity by first-principles molecular dynamics including electron-phonon and electron-electron scattering. We find that the measured resistivity of hcp iron increases almost linearly with temperature, and is consistent with our computations. The results constrain the resistivity and thermal conductivity of hcp iron to $\ensuremath{\sim}80\ifmmode\pm\else\textpm\fi{}5\text{ }\text{ }\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\text{ }\mathrm{cm}$ and $\ensuremath{\sim}100\ifmmode\pm\else\textpm\fi{}10\text{ }\text{ }\mathrm{W}\text{ }{\mathrm{m}}^{\ensuremath{-}1}\text{ }{\mathrm{K}}^{\ensuremath{-}1}$, respectively, at conditions near the core-mantle boundary. Our results indicate an adiabatic heat flow of $\ensuremath{\sim}10\ifmmode\pm\else\textpm\fi{}1\text{ }\text{ }\mathrm{TW}$ out of the core, supporting a present-day geodynamo driven by thermal and compositional convection.