Marcelo Castier


From this page, you can download XSEOS - Excess Gibbs Free Energy Models and Equations of State - a freely available Excel add-in to compute thermodynamic properties using many traditional and modern thermodynamic models. These properties are programmed as functions in Visual Basic for Applications (VBA), totaling about 22000 lines of code. Users can call these functions from their Excel spreadsheets.

XSEOS has open source code and is distributed under the GNU General Public License, version 3. Therefore, it is an expandable platform and will hopefully contribute to the exchange of experiences in the teaching of Chemical Engineering Thermodynamics. XSEOS runs in Excel, which is part of the Microsoft Office suite, available from Microsoft resellers.

Click here to download a zipped file that has five files inside: the XSEOS manual, the Excel add-in, its installer (only necessary for Excel 2003), a sample spreadsheet, and a specific sample file with surface tension examples. Please, unzip all files in the same directory (preferably C:\XSEOS) and follow the installation instructions provided in the manual. The manual also gives hints on how to use the program and lists all thermodynamic models currently available in the package. The current version of XSEOS has been successfully tested in Excel 2003, 2007, and 2010.

After installation and before reading the manual, you may wish to watch a few movies that illustrate how to use the program and try some of the examples by yourself using the Excel templates provided. To watch the movies you will need Adobe Flash Player. If not available in your computer, you can install it from here.

The movies and templates are organized according to the type of calculation and thermodynamic model.

Depending on your computer settings, the movies may look blurred. If this happens, right-click your mouse once the movies starts and then click on "Zoom in".

Type of Calculation

Activity coefficients: movie and Excel template

Activity coefficients with group contribution method: movie and Excel template

Enthalpy of vaporization: movie and Excel template

Excess properties: movie and Excel template

Boiling temperature: movie1 and Excel template1 ; movie2 and Excel template2

Bubble point with activity coefficients: movie and Excel template

Bubble point with fugacity coefficients: movie and Excel template

Isenthalpic expansion: movie and Excel template

Isothermal flash: movie and Excel template

Parameter fitting of excess Gibbs free energy models: movie and Excel template


Thermodynamic Model

Margules 2-, 3-, and 4- suffix: movie and Excel template

Mattedi-Tavares-Castier (MTC):  movie and Excel template

NRTL: movie and Excel template

Peng-Robinson equation of state: movie1 and Excel template1 ; movie2 and Excel template2

Predictive Soave-Redlich-Kwong (PSRK): movie and Excel template

Regular solution theory: movie and Excel template

Soave-Redlich-Kwong: movie and Excel template

UNIFAC: movie and Excel template

UNIQUAC:  movie and Excel template

van der Waals: movie and Excel template