MatCalc version: 5.0 - …
Author: E. Kozeschnik
Created: 2011-07-05
Revisions:
In this document, general considerations for equilibrium and non-equilibrium thermodynamic simulations … are discussed.
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Before actually going into the software to perform the simulation, do make sure you clearly know which problem you want to solve. Setup a thermodynamic simulation as simple as possible in order to avoid unnecessary computational effort and artifacts that might come from incomplete or missing thermodynamic data. But do not make the system too simple, otherwise you run into danger of missing the answers that you are seeking.
When setting up a thermodynamic simulation in MatCalc, you commonly proceed with the following steps:
In the GUI version of MatCalc, all information about the thermodynamic system, all simulation results, and also the position and order of windows is stored in a MatCalc workspace. The file extension is '*.mcw'. Alternatively, you can store your results in a binary file, which avoids all GUI relevant information and only stores the simulation setup and all results. The binary file extension is '*.mcb'.
The definition of the thermodynamic system in MatCalc is a most relevant step in the simulation setup. This step defines the possible elements that take part in any kind of simulation, as well as the possible phases. Any element or phase that you miss to define in this step cannot be added or included later on without destroying all simulation results.
After definition of elements and phases of the database, the chemical composition of the thermodynamic system must be set. In the 'Nominal composition' dialog, the amount of elements can be entered in
By default, one of the elements is set as the reference element. This definition is usually done in the database with the command REFERENCE_ELEMENT.
The last step before actually performing the equilibrium simulation is to initialize the MatCalc variables and parameters with some reasonable starting values. This is done with the 'Set start values' command in the 'Calc' menu.
It is possible, to leave out this step, however, the simulation sometimes does not converge and will deliver undefined results.
You can use this command multiple times to improve the initial estimates.
The 'Set start values' command is used whenever the simulation state is undefined, such as, for instance, after reading the thermodynamic database. You can also use it in case you have trouble with convergence of equilibrium simulations. Several calls of this function (and eventually a change of temperature to higher values) can be beneficial for convergence.
Perform the equilibrium simulation with the 'Equilibrium …' command from the 'Calc' menu. Enter the desired temperature and pressure1) and start the simulation with the 'Go' button.
Important …
- OK -
if the simulation was successful, report a * Warning *
, if you should recheck the result, and report * ERROR *
, if no solution was found.
If you do not check the status of your simulation results, you are running danger of using undefined results.