Variation of the Gruneisen parameter with density for the different models and fits. The green line has been fit to experimental data from Anderson (2007) and Anderson & Isaak (2003) using our EOS with t_min = 1.94, δ_t = 3.89. The PREM curve was fit to ambient pressure values for ɛ-Fe given in Dubrovinsky et al. (2000) (γ₀ = 1.78 q₀ = 0.69). The Gruneisen parameter from the Tillotson EOS can be seen to have a completely different behavior than the rest.