FIGURE 2. Theoretical fractionation of silicon isotopes between silicate and metal as a function of temperature.

Equilibrium ³⁰Si/²⁸Si fractionation ( = 1,000 ln_{silicate-metal}) between silicate and metal is estimated from lattice-dynamics modelling of Mg₂SiO₄-olivine and body-centred cubic Fe₃Si. The lower (black) curve is calculated assuming Si-atom vibration at 10 THz in the Fe₃Si structure. The upper (grey) curve assumes Si-atom vibration at 7.5 THz in Fe₃Si. The dashed curves at temperatures above 1,200 °C (1,473 K) indicate extrapolation beyond the 1 atm melting point of Fe₃Si.