The Equilib Module

FactSage contains many modules. The major ones for daily work are Equilib and Phase Diagram.

In the Equilib module, global Gibbs energy minimization is used to determine the equilibrium state of a complex chemical system defined by its chemical composition, temperature and pressure. Equilib is easy to use: First, the chemical system has to be defined in the Reactants window:

As it can be seen, reactants can be defined in various ways: By inserting the mass or the molar amount, or even by a combination of both. Additionally, elements (Fe. Cr. Ni. C) can be used as well as chemical formulae (N2, O2).

Next, the calculation conditions have to be specified in the Menu window:

The user can choose the possible products to be considered in the calculation. If you are interested in the thermodynamic equilibrium, you can simply choose all possible products. If you want to suppress a phase since you are sure that it does not form due to limited reaction kinetics (e.g. Graphite in the Fe-C system), you can simply omit the phase from the calculation. Chemical equilibrium can be calculated for a system that is defined with regard to temperature, pressure (or volume), enthalpy and total amounts and/or equilibrium activities of any phase constituent in the system. Several calculations can be done at once, where e.g. temperature is varied. In the figure above, temperature is varied between 500 and 1000°C with a step size of 50°C, resulting in 11 calculations. Other conditions for an equilibrium can also be set, for example that a certain phase is formed when temperature or composition changes or a Scheil cooling curve.

The result is first presented in a simple table and can be used in the integrated postprocessor to prepare a graphical output. Of course, the results can also be exported to other applications, e.g. into an Excel® spreadsheet. Below is a (shortened) results table and a screenshot of the Figure module. As example, the amounts of all stable phases is shown as function of temperature.

Do you want to try a simple web-based Equilib calculation? Use the demo Equilib-Web feature developed by our partners at ThermFact/CRCT!

Interested in further information? Check out the information about Equilib on factsage.com!

 *T = 881.94 C
 P = 1 bar
 V = 0 dm3
 
 STREAM CONSTITUENTS          AMOUNT/gram
 Fe                            8.2000E+01
 Cr                            1.8000E+01
 Ni                            1.0000E+01
 C                             5.0000E-02
 
                              EQUIL AMOUNT  MASS FRACTION     ACTIVITY
 PHASE: FCC_A1#1;#2;#3            gram
 CrC                           4.6472E-02     4.2228E-04     3.5275E-03
 FeC                           2.0897E-01     1.8988E-03     1.2011E-05
 NiC                           2.5265E-02     2.2958E-04     1.6154E-06
 Cr1Va1                        1.7962E+01     1.6322E-01     1.9528E-01
 Fe1Va1                        8.1828E+01     7.4355E-01     7.4085E-01
 Ni1Va1                        9.9790E+00     9.0677E-02     5.5347E-02
 TOTAL:                        1.1005E+02     1.0000E+00     1.0000E+00
    Site fraction of sublattice constituents:
    Cr                         0.17441       Stoichiometry = 1
    Fe                         0.73976
    Ni                         8.5836E-02
    -------------------------------------------------------------------
    C                          2.0973E-03    Stoichiometry = 1
    Va                         0.99790
    System component         Mole fraction  Mass fraction
    Ni                         8.5657E-02     9.0868E-02
    Fe                         0.73821        0.74512
    Cr                         0.17404        0.16356
    C                          2.0929E-03     4.5434E-04
    Neel temperature = -195.08 C
    Average magnetic moment/atom = 0.26357
 PHASE: M23C6                     gram      MASS FRACTION     ACTIVITY
 Cr20Cr3C6                     0.0000E+00     5.9723E-01     2.1437E-03
 Fe20Cr3C6                     0.0000E+00     1.8366E-01     3.1322E-15
 Ni20Cr3C6                     0.0000E+00     6.1375E-03     1.0076E-41
 Cr20Fe3C6                     0.0000E+00     1.5428E-01     3.5964E-05
 Fe20Fe3C6                     0.0000E+00     4.7420E-02     5.2548E-17
 Ni20Fe3C6                     0.0000E+00     1.5841E-03     1.6903E-43
 Cr20Ni3C6                     0.0000E+00     7.3548E-03     3.8193E-09
 Fe20Ni3C6                     0.0000E+00     2.2598E-03     5.5805E-21
 Ni20Ni3C6                     0.0000E+00     7.5471E-05     1.7951E-47
 TOTAL:                        0.0000E+00     1.0000E+00     1.0000E+00
    Site fraction of sublattice constituents:
    Cr                         0.76969       Stoichiometry = 20
    Fe                         0.22315
    Ni                         7.1542E-03
    -------------------------------------------------------------------
    Cr                         0.78857       Stoichiometry = 3
    Fe                         0.20187
    Ni                         9.5597E-03
    -------------------------------------------------------------------
    C                          1.0000        Stoichiometry = 6
    System component         Mole fraction  Mass fraction
    Ni                         5.9228E-03     7.8233E-03
    Fe                         0.17478        0.21966
    Cr                         0.61240        0.71660
    C                          0.20690        5.5923E-02
 PHASE: BCC_A2#1;#2               gram      MASS FRACTION     ACTIVITY
 CrC3                          0.0000E+00     4.5556E-05     2.7455E-26
 FeC3                          0.0000E+00     1.4678E-04     9.4888E-26
 NiC3                          0.0000E+00     9.2878E-06     5.8584E-26
 Cr1Va3                        0.0000E+00     2.2074E-01     4.2513E-01
 Fe1Va3                        0.0000E+00     7.3185E-01     7.4303E-01
 Ni1Va3                        0.0000E+00     4.7209E-02     3.4267E-02
 TOTAL:                        0.0000E+00     1.0000E+00     9.7882E-01
 PHASE: LIQUID#1;#2               gram      MASS FRACTION     ACTIVITY
 Fe                            0.0000E+00     6.7127E-01     4.4644E-01
 C                             0.0000E+00     2.4320E-03     7.1279E-07
 Cr                            0.0000E+00     2.6170E-01     1.3307E-01
 Ni                            0.0000E+00     6.4592E-02     3.1027E-02
 TOTAL:                        0.0000E+00     1.0000E+00     7.2799E-01
 PHASE: CEMENTITE                 gram      MASS FRACTION     ACTIVITY
 Cr3C                          0.0000E+00     8.1418E-01     2.6015E-01
 Fe3C                          0.0000E+00     1.8282E-01     3.4403E-03
 Ni3C                          0.0000E+00     2.9944E-03     3.7805E-07
 TOTAL:                        0.0000E+00     1.0000E+00     4.5825E-01
 ********************************************************************
      Cp             H             S             G             V
     J.K-1           J           J.K-1           J            dm3
 ********************************************************************
  6.70694E+01   6.76446E+04   1.58581E+02  -1.15530E+05   0.00000E+00
 
 Cut-off limit for phase activities = 1.00E-75
 
 Databases: FSstel 7.0, FactPS 7.0                                                       
 Data Search options: exclude gas ions; organic CxHy.. X(max) = 2; min soln cpts = 2