Calculating an Equilibrium

This topic explains how to calculate an equilibrium in POLY. To calculate an equilibrium means to calculate the equilibrium composition of your system, given a full specification of conditions that reduce the degrees of freedom of the calculation to zero.

If you are running a network client installation of Thermo‑Calc and cannot enter the POLY module, this may be because all the license instances on that the license server makes available have been checked out.

POLY Module Commands

  1. Define your system.

    Defining a System in Console Mode

  2. Go to the POLY module. At the SYS prompt, type GOTO_MODULE and enter POLY.
  3. Use SET_CONDITION followed by conditions and value assignments to set the conditions of your calculation. For example, to set temperature, pressure, initial composition and system size for a Fe-Cr-C system, you might enter the following:

SET_CONDITION T=1200 P=1E5 W(CR)=0.18 W(C)=0.0013 N=1

This sets the temperature (T) to 1200 K, the pressure to 1 bar (100,000 Pascal), the mass fraction of Cr to 18 mole percent, the mass fraction of C to 0.13 weight percent, and the total amount of material to 1 mole. The fraction of Fe in the system is calculated from the fractions of Cr and C. You have to set the fraction of all the components in your system except one.

  1. Use COMPUTE_EQUILIBRIUM to run the calculation.
  2. Use LIST_EQUILIBRIUM to see the results of the calculation.