Get started with THERMOCALC

This page gives a brief introduction for those who have never used THERMOCALC before. If you already know what to expect from THERMOCALC, you may be looking for the Download guide or Help page.

On this page:

Before you start calculations

To get started with the core THERMOCALC software:

  • If you’re looking for the the SCOlP and COlP barometers of Ziberna, Green & Blundy (2017), leave this page now and go directly here. Otherwise….
  • Determine how phase equilibrium calculations could be used to address your particular problem. You might want to see:
  • Find out which (if any) existing sets of HPx-eos can be used for the calculations you want to do.

Starting a calculation

  • Use the THERMOCALC download guide to download the THERMOCALC software, and to set up a working directory (folder) for your project, containing a prefs file, scriptfile, dataset file and axfile.
  • Give your scriptfile a suitable root name, <project>, to reflect your project (it must be called tc-<project>.txt) .
  • Open the prefs file, tc-prefs.txt:
    • set the script “scriptfile <project>”, so THERMOCALC can find the scriptfile;
    • set the script “dataset <xx>”, where xx is the version of the dataset file you have downloaded (e.g. 62 or 633), so THERMOCALC can find the dataset file.
  • Open the scriptfile. Set the script “axfile <system>“, where <system> is the root name of the axfile you have downloaded (e.g. KNCFMASHTOCr), so THERMOCALC can find the axfile.
  • If you’re confident to do so: make sure you have the THERMOCALC excutable in a convenient place on your system, navigate to your project directory and call THERMOCALC from the command line.
  • Otherwise:
    • Windows users can simply put THERMOCALC into their project directory and double-click to start.
    • Mac users: you must use THERMOCALC via the command line:
      1. Put THERMOCALC into your project directory.
      2. Open a Terminal window. You can find Terminal in Applications > Utilities.
      3. Tell Terminal to look in your project directory, by typing “cd <path-to-working-directory>” followed by return (⮐). To get the <path-to-working-directory>, you can simply drag the little folder icon from the top of your working directory Finder window into the Terminal window (see figure below).
      4. Tell Terminal to run THERMOCALC by typing “./<name-of-THERMOCALC-app>”, e.g. “./tc347”, followed by return (⮐).
  • Type “kill” followed by return (⮐) at any time to stop the calculation.
On the Mac: directing a Terminal window to the project directory (“cd …”) and starting THERMOCALC 3.46 (“./tc346”)

Running calculations

Paradigm for calculations

THERMOCALC is essentially interested in phase assemblages. At the start of each calculation, the user must choose a subset (assemblage) of the phases in the axfile. To calculate a phase diagram involving multiple phase assemblages, the user must build up the diagram manually through calculations on many assemblages.

Thermodynamic input for phases

THERMOCALC reads in the phases that the user will want to consider from the axfile. The phases listed in the axfile include both pure end-members and solution phases (solid solutions or variable-composition fluids). Pure end-members are taken directly from the Holland & Powell dataset, which is read from the dataset file. A solution phase is represented by an x-eos, which THERMOCALC constructs using information in the axfile. This information includes:

  • instructions for making each end-member from one or more end-members in the Holland & Powell dataset;
  • instructions for describing the energetics of mixing these end-members (activity-composition relations).

THERMOCALC automatically prints full human-friendly details of the HPx-eos in the -it output file, and users are encouraged to look in this file for a greater understanding of the assumptions made about the solution phases. Details of the properties of end-members from the Holland & Powell dataset can be found by running THERMOCALC in calcmode 0.

Scripts versus interactive behaviour

Calculations are controlled through a mixture of scripts set in the scriptfile and interactive prompts. A new user can use THERMOCALC interactively to get a feeling for how it works, but a more experienced user will probably make heavy use of scripts. Different specialist scripts are needed for the different calculation modes offered by THERMOCALC, which also have their own types of output. Find out more about using the individual calculation modes by following links from here.

In interactive mode, answers to prompts can be “y” or “n” (“yes” or “no”), return (⮐), a value, or a list of values. Or type “kill” to end the run.


The output depends on the calculation type, but in general we are moving towards having general, standardised .csv output as far as possible, with an option to plot most phase diagram output in DRAWPD. There should always be an -it file containing details of the HPx-eos used, and all phase diagram calculations should give extensive thermodynamic output in the -ic file.

Getting help

Start with the THERMOCALC help page.


Please contact us if you think you have found a bug, or something that doesn’t function as it should. We try to fix problems quickly, but if no one tells us about them, we may never discover them for ourselves.

Have fun!