Calculating an Equilibrium with a Fixed Phase

There are many ways to calculate equilibriums in Thermo‑Calc. The following is one example.

You can calculate an equilibrium that has a certain amount of a certain stable phase. Use CHANGE_STATUS and choose Phase to specify the phase and the amount of that phase (in normalized mole number) that you want to set as fixed. For example, if you want to find out at what temperature a system starts to melt, enter the following:

CHANGE_STATUS PHASE LIQUID=FIX 0

You must leave the state variable whose equilibrium value you are interested in unspecified. However, if you have already specified that state variable, you can make it unspecified again by using SET_CONDITION and set that state variable to NONE. For example, if you have given temperature a value, you can type:

SET_CONDITION T=NONE

The calculated equilibrium includes the value of the unspecified variable at which the equilibrium enters the phase that is fixed.

For an example where an equilibrium is calculated with a fixed phase, see Console Mode example tcex07.