Investigation of the crystallization of liquid iron under pressure: Extrapolation of the melt viscosity into the megabar range

Measurements are made of the average size of the crystallites in Fe samples obtained by rapid quenching from the melt at high pressures up to 95 kbar. The data obtained make it possible to estimate the pressure dependence of the viscosity of the Fe melt. It is found that, contrary to the existing empirical models, the viscosity increases along the melting curve under compression. Extrapolation of the pressure dependences obtained to the P, T conditions corresponding to the Earth’s core gives extremely high values of the viscosity, ranging from 10² Pa·s up to 10¹¹ Pa·s in the outer core, which suggests that the inner core is in a glassy state. The possibility that the lines of vitrification and melting of substances intersect in the megabar range is discussed. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 469–474 (25 September 1998)