Berlin 2012 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 45: Computational Materials Modelling VI - Thermal Conductivity and Transport

MM 45.2: Talk

Thursday, March 29, 2012, 10:30–10:45, TC 006

Thermal conductivity of minerals at the Earth’s core-mantle boundary from equilibrium molecular dynamics — •Volker Haigis¹, Mathieu Salanne², and Sandro Jahn¹ — ¹GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany — ²UPMC Université Paris 06 and CNRS, UMR 7195, PECSA, 75005 Paris, France

The thermal conductivity at the Earth’s core-mantle boundary is an important geophysical parameter which governs the heat flux across the boundary and thus influences the dynamics of both core and mantle. However, conductivities at the relevant temperatures and pressures cannot be measured with present-day experimental techniques. Hence a computational approach is desirable. We report thermal conductivities of fcc MgO and MgSiO₃ in the perovskite and the post-perovskite structure at conditions representative of the Earth’s lowermost mantle, obtained from equilibrium molcular dynamics. Using an advanced ionic interaction potential [1], the full conductivity tensor was calculated by means of the Green-Kubo method, and the conductivity of MgSiO₃post-perovskite was found to be significantly anisotropic. Assuming an iron-free mantle composition with x_MgSiO3 = 0.66 (in the post-perovskite structure) and x_MgO = 0.34, we predict the average thermal conductivity at the core-mantle boundary to be (24.3 ± 1.8) W/(mK). Based on experiments [2], we expect that a realistic amount of iron impurities reduces the conductivity to (12 ± 1) W/(mK).

[1] S. Jahn, P. A. Madden, Phys. Earth Planet. Int. 162, 129 (2007)

[2] G. M. Manthilake et al., PNAS 108, 17901 (2011)