Computer Science
Scientific paper
Oct 1974
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1974gecoa..38.1527g&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 38, Issue 10, pp.1527-1548
Computer Science
5
Scientific paper
For a phase at equilibrium in which two cation species are partitioned ideally between two sub-lattice sites, the excess functions of mixing (free energy, enthalpy and entropy) are directly related to the bulk composition of the phase and G E °( T , P ), the standard-state intra- crystalline exchange free energy. If the phase is not at equilibrium internally, an additional ordering parameter is necessary to fix the excess free energy of mixing, G mix EX , unambiguously. Conversely, for any fixed G mix EX there exists an infinity of possible intracrystalline cation dis- tributions, only one of which is the equilibrium distribution for the specified temperature and pressure. As ideal intraphase cation ordering becomes more pronounced, G mix EX decreases. In response, the total free energy of mixing for the phase decreases progressively for non-end member compositions, approaching, at the limits of ordering, values appropriate for stabilizing compounds of intermediate composition. The model-dependent activity coefficient for component A in the phase, A T , can be calculated for any bulk composition, X A T , either from G mix EX directly or from more basic equations involving the interrelation of chemical potentials at equilibrium. A general form for A T is ln , where Xj denotes the mole fraction of species j in site . The first term on the right-hand side of this equation is the contribution to A T from ideal intracrystalline partitioning, and is common to the several theories lately presented to model intraphase cation partitioning. It can be shown rigorously that this term contributes to a negative deviation from ideality for the bulk phase. The second term is the contribution to the macroscopic activity coefficient from non-ideal intraphase partitioning, and is related to an enthalpy of mixing, H mix N in excess of that resulting from ideal inter-site cation ordering. While the expression represented by Y can take several functional forms, the additional enthalpy can be evaluated explicitly for specific non-ideal partitioning models from the relation . In those cases, G mix EX can also be determined exactly.
No associations
LandOfFree
On calculating activity coefficients and other excess functions from the intracrystalline exchange properties of a double-site phase does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with On calculating activity coefficients and other excess functions from the intracrystalline exchange properties of a double-site phase, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and On calculating activity coefficients and other excess functions from the intracrystalline exchange properties of a double-site phase will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-792608