The Import sub-program in EosFit7c allows you to import EoS from other databases and files. At this time there are two file formats supported:
- From the Thermocalc database (Holland & Powell, 2011) in the form of a text file, normally with a name like tc-ds62.txt
- From a table of V (or linear) values as a function of P and T.
Import routines for other popular file formats can be added in future. Contact us with the details of the files you need to import and we will explore the possibilities.
The import utility can be started from the main command prompt, or from within the input utility. A list of available file types that can be imported is listed, and you can choose which one to import.
1: Thermocalc import
- You must have the Thermocalc dataset as a text file on your computer. EosFit7c supports input from tc-ds62.txt, and maybe later versions. You can download the datasets from the Uni-Mainz Thermocalc pages.
- EosFit7c does not import from earlier Thermocalc datasets (like ds55). For these, use the Input command in EosFit7c to create a new EoS with the parameters from Thermocalc, and then save it as a .eos file.
- Important: the model for Landau-like phase transitions in Thermocalc is subtly different from that used in EosFit7. Therefore, if you import an EoS with a Landau phase transition (e.g. quartz) EosFit7 will calculate volumes at P and T that may differ by about 0.05% from those obtained in Thermocalc.
- When you select 'Thermocalc import', you must open the database file from the file browser.
- Then you select the phase you want by writing the exact Thermocalc abbreviation for the phase that you want. These abbreviations are listed in Holland and Powell (2011).
- If your phase is found, you will see a summary of the imported EoS parameters:

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This is the EoS imported for Forsterite (abbreviation fo)
The title is set to indicate the source of the data
And the comments explain the conversion of values from the Thermocalc database.
The composition and molar volume from the Thermocalc database are used to set the room-P,T density.
Check the values before finishing the Import by answering Y to the last question.
You can modify any of the values, add further values (e.g. the shear modulus) or modify the comments with the input command.
The imported EoS is not automatically written to an .eos file. If you want to save it to file use the save command.
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2: PVT tables import
This utility allows you to import a table of volumes as a function of P and T from a text file. This is useful for materials, such as fluids or gases, which do not have simple EoS of the type supported in EoSFit7.
After you import a PTV table you can perform all types of EoS calculations in EoSFit7c, but they cannot be used in EosFit7-GUI or the EoSFit7-calculator.
Below is an example of a table file.
- Rows starting with text at the top of the file are ignored by EosFit7c; they can be used to record information.
- Data can be arranged as rows of constant pressure, or rows of constant temperature
- The example has rows of constant pressure, and the description is written for this format.
- If you have a file with rows of constant temperature, just exchange the words 'temperature' and 'pressure' in the description here.
- The first row of numbers are the temperature values for each column
- Each row of data starts with the pressure value, followed by the values of volume.
- There is no special 'end' character. Punctuation like ':' is not allowed.

When you select 'Table import', you must open the table file from the file browser, and then answer the questions about the table:

How it works
- EosFit7c does not fit the data. Therefore it does not store or determine parameters such as bulk modulus or V0:
- Therefore no parameters are displayed when you type the param command.
- There is no way to save the EoS as an .eos file because there are no parameters!
- And you cannot 'refine' the EoS to data, because there are no parameters to refine!
- EosFit7c performs EoS calculations by interpolating between the table values:
- The first interpolation is done in pressure, at the T values immediately below and above the requested temperature. This interpolation is done locally with a Murnaghan EoS.
- The second interpolation is done linearly in temperature.
- Important:
- In order to obtain accurate values of V or its derivatives like K or α, it is necessary to have an appropriate step size in P and T values in the table. The user must experiment to find what step sizes in P and T values give the accuracy required! Use the props command to test.
- The higher the order of a derivative, the less accurate it will be. Therefore V values are more accurately interpolated than K, which are in turn more accurate than K' values.
- Interpolation cannot be performed at the edges of the table, or beyond the range of P and T in the table. Therefore you should prepare a table that extends beyond the P and T values of interest. This includes preparing a table to negative pressures, to make calculations at P = 0, as in the example shown above.