Compression curves of the different models and fits. The green line has been fit to the ɛ-Fe data from Dewaele et al. (2006) using the Varpoly EOS (). The phase change at around 16 GPa, from α-Fe to ɛ-Fe is clearly seen in the figure. To reproduce the density and pressure at the center of Earth, the fits to pure iron (compression, Hugoniot, and Tillotson) requires an unrealistically high central temperature of around 14 000K, while the PREM-fit requires a more realistic temperature of around 5300K.