ChemApp contains subroutines that enable the status of phases or constituents to be changed; that is, to be either excluded from or re-entered into an equilibrium calculation (see Table 10). The default status is that stored in the thermodynamic data-file. The status for a phase can be changed implicitly, dependent on the explicit changes of the statuses of its constituents. For example, if all constituents of a phase are made dormant, the phase will also be dormant.
Whereas complete phases can always be set ENTERED, DORMANT or ELIMINATED, some restrictions apply for phase constituents (see the notes for TQCSPC).
A common reason for changing the status of a phase is for instance the desire to calculate a metastable equilibrium (see TQGSP) or to increase the computational speed in systems containing miscibility gaps (see Appendix E.2).
Table 10: ChemApp subroutines for changing the status of phases and constituents
|TQGSP|| Gets the status of a phase
|TQCSP|| Changes the status of a phase
|TQGSPC|| Gets the status of a phase constituent
|TQCSPC|| Changes the status of a phase constituent
Table 11: Possible statuses for phases and constituents
|ENTERED|| The phase or constituent is included in the equilibrium
calculation. An included phase is not necessarily stable at
|DORMANT|| The phase or constituent is excluded from the mass balances (it will
appear with zero amount at equilibrium), but its activity is
calculated. If the calculated activity for a phase is greater than
one, it would be stable if entered.
|ELIMINATED|| The phase or constituent is ignored in the equilibrium
|ChemApp Programmer's Manual, Edition 3.6||© GTT-Technologies, 2003|