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Paul Scherrer Institut PSI GEM Software (GEMS) Home

Paul Scherrer Institut
5232 Villigen PSI, Schweiz/Switzerland
Tel. +41 56 310 21 11
Fax. +41 56 310 21 99

E-Mail: gems2.support@psi.ch

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GEMSFITS Software: 

Examples and Test Projects

The GEMSFITS test suite is a set of examples for different parameter optimization problems. The projects can be used as tutorials for learning GEMSFITS and as a source for different types of optimization setups. It is recommended to copy-paste different sections from fitting Tasks found in the Tests projects into the users own optimization project and do the necessary modifications.

The tests are included into GEMSFITS installer (see "/Tests/"); they will be automatically copied in the user tests directory upon the first installation; upon the upgrade, the folder will be overwritten.

Each project is opened in GEMSFITS by Open Project ... and clicking on the *.pro file found in the folder named after the test.

Each test project comes with pre-formated experimental data found in the /dbimport/ folder, the exported GEMS3K chemical system files, and the GEM-Selektor project both found inside the /GEMS/ folder for each test example.

It is recommended that the user uses the pre-formated experimental data files distributed with the text projects as templates and doing necessary changes for loading their own experimental data into the fitting project.


Test fitting project
Aqueous-Al Fitting multiple aqueous species independent (type F) and reaction constrained (type R). For one of the reactions (AlOH+2) the logK values are calculated using a logK function of water density (logK_dRHOw function and coefficients described in LogKFun) and literature parameters, and for a second one (NaAl(OH)4@) it uses the logK values from the input system file calculated in the initial step.

The test also uses the nested functionality to fix the calculated pH at each optimization step to the measured one by titrating NaOH and HCl.
Fitting Calcite-Strontianite solid solution interaction parameters against excess Gibbs energy data, without using full equilibrium calculations (UseEqC set to -1 - no equilibrium, instead of 1 with equilibrium)
CSH-solid-solution Fitting G0 of end members and non ideal interaction parameters for a CSH solid-solution against measured Ca(aq), Si(aq), Ca/Si in solid, and mean silicate chain length (mChainL).
Fitting G0 of sorption sites against Rd (partition coefficient) measured values form experiments, with and without the presence of air.
Fitting Pitzer interaction parameters as a function of T and P against synthetic experimental data from Archer et al. (1992). Using 120% +- bounds from initial values for the parameters (PBPerc set to 120). !!convergence problems, needs to be checked / updated.
A. Test example for fitting Ti in quartz regular solid solution model parameters against experimental data of Thomas et al., (2010) and Wark and Watson (2006). TiQ_normal.pro

B. Using the fitted parameters from TiQ_normal for doing inverse modeling calculations determining the T & P of formation of quartz crystals based on their Ti content. TiQ_inverse.pro

Results are found in Inv. Mod. Results tab of the Results window.

(always under construction)

Last updated:  03.08.2018 DM

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