DISLOCATION MELTING OF IRON AND THE TEMPERATURE OF THE INNER-CORE BOUNDARY, REVISITED

The melting point T(m) of iron at conditions of the Earth's inner core boundary (ICB) has been calculated from the dislocation theory of melting in metals. These calculations take into account the effects of pressure at ICB conditions and of possible freezing point depression resulting from dilution of pure iron in the outer core. Monte Carlo calculations have been used to estimate the uncertainties introduced by uncertainty in the geophysical parameters that are used in the calculations. With this approach T(m) of pure epsilon-Fe at a pressure of 330 GPa and without freezing point depression is 6160+/-250K, and 6110K for a 1000K freezing-point depression, T(m) of pure gamma-Fe is not significantly different; these values agree well with shock-wave determinations of T(m). The estimated temperature of the ICB is lower by the freezing point depression, perhaps by 500-1000K.