1. In this paper mainly the quantity x=[Li]/([Li]+[Nb]) will be used to characterize melts or crystals. This x is equal to the Li2O mole fraction. Alternatively the ratio Li/Nb=R can be employed. Both systems are related to each other by x=R/(1+R) and R=x/(1 ? x). Subscripts m and c will be used to designate melt and crystal, respectively
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