Читать книгу Geochemistry - William M. White - Страница 123
3.8.2 Local charge balance model
ОглавлениеYet another model for the calculation of activities in ideal solid solutions is the local charge balance model. A common example is the substitution of Ca for Na in the plagioclase solid solution (NaAlSi3O8–CaAl2Si2O8). To maintain charge balance, the substitution of Ca2+ for Na+ in the octahedral site requires substitution of Al3+ for Si4+ in the tetrahedral site. In this model, the activity of the end-member of phase component is equal to the mole fraction of the component (see Example 3.5).
