Distributions of transition metals between crystals and melts

8 Distributions of transition metals between crystals and melts 

If two phases are in equilibrium with one another at some temperature and pressure, a transition metal ion will be distributed between the phases in such a way as to minimize the free energy of the two-phase assemblage. This should generally result in the transition element being concentrated in the phase giving largest crystal field stabilization energy. 

Consider two phases a and /J containing octahedral sites available for cation occupancy. The distribution of cations between these sites will depend on the relative values of the CFSE for the two sites. If CFSE CFSE 1, then the Nemst distribution coefficient, D, expressing the concentration ratio of transition element, M, between the two phases 

The data in table 2.5 show that CFSE s for divalent cations increase in the order Mn Fe Co Ni. From this the following orders are predicted for the distribution coefficients and the interphase (intercrystalline) partition coefficients  

Similarly, the distribution coefficients for trivalent cations in octahedral sites are predicted to show the order  

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