The GEMS default Thermodynamic Database (TDB) is included for a broader applicability of GEM-Selektor and GEMS3K codes.
TDB includes the PSI-Nagra chemical thermodynamic database converted into GEMS DComp/ReacDC formats (default).
TDB also includes the SUPCRT92
(Slop98.dat) dataset imported into GEMS DComp format (complementary).
Third-party TDB plugins for specific applications (e.g. cement
chemistry, nuclear engineering, ore petrology) are available.
In GEM-Selektor code, the thermodynamic data for DCs is
automatically corrected for temperature and pressure of interest.
Thermodynamic data for wide T,P ranges can be exported into GEMS3K I/O files and thus into coupled reactive transport codes.
GEM-Selektor v.3 package is distributed with a default chemical
thermodynamic database that consists of three parts: (i) "psi-nagra";
(ii) "supcrt"; and (iii) "3rd-party", selectable upon creation of
projects within GEMS "Elements" dialog.
These parts can be selected separately or simultaneously when a new
GEMS modeling project is created.
(i) The "psi-nagra"
part has been imported from the PSI/Nagra 12/07 chemical thermodynamic database, which is a recent update of the previous Nagra-PSI chemical
thermodynamic data base 01/01. This database covers the needs of geochemical modelling
related to the nuclear waste
disposal. In order to make the database also usable at
moderately elevated temperatures
and pressures, it was merged with a subset of the "supcrt" database.
(ii) The "supcrt"
part consists of the imported very popular SUPCRT92 (Slop98.dat)
dataset, which enables calculation of aqueous equilibria at
temperatures up to 1000 oC
and pressures up to 5 kbar for a wide range of species and chemical
elements, also those not available in the "psi-nagra" part. The SUPCRT92
dataset that relies on the open SUPCRT92 code and the revised
HKF EoS (Helgeson- Kirkham- Flowers
of state) is at present a "de facto" standard in geochemistry, supplied
also completely or in part with many other codes (e.g. ChemApp, EQ3/6, GIBBS/Hch,
(iii) The "3rd-party" part (optional) is represented by one or more third-party databases
covering specific application fields (e.g. Cemdata'07 or HERACLES). The
respective files can be downloaded separately and added into the
default database folder in the actual GEM-Selektor installation.
GEM-Selektor supports a unique "hybrid" structure of thermodynamic database, comprised of the DComp and ReacDC formats. TDB parts in DComp format contain 'thermochemical' and/or 'equation of state' data for Dependent Components (DC). TDB parts in ReacDC format define the thermodynamic data for a DC via the properties of its reaction with other DCs with already known properties. The respective modules of GEM-Selektor code provide efficient tools for internally consistent extension of project thermodynamic databases, which is also enhanced by standalone codes such as PMATCHC.
files in the default database folder ("/DB.default/")
are write-protected in GEM-Selektor code in order to prevent an unitentional data loss or
corruption, and to ensure a backward compatibility between different
projects. More technical details about that can be found in
the GEM-Selektor help pages.
The LES PSI Thermodynamics Group maintains the PSI/Nagra database provided as the default dataset with the GEM-Selektor code and oriented mainly to specific nuclear waste management applications. However, the GEM-Selektor code itself is not application- or database-specific, so the main limitation of its usage is the lack of internally consistent input thermodynamic data. These can be compiled by other people, converted into GEM-Selektor format, and distributed as third-party chemical thermodynamic databases.
Helgeson H.C., Kirkham D.H. and Flowers G.C. (1981): Amer. J. Sci. v. 281, p. 1249-1516.
Johnson J.W., Oelkers E.H. and Helgeson H.C. (1992): Comput. Geosci. v. 18, p. 899-947.
Shock E.L., Sassani D.C., Willis M. and Sverjensky D.A. (1997): Geoch. Cosmoch. Acta v. 61, p. 907-950 (and references therein).