The solution databases (for solutions of oxides, salts, metals, etc.) have all been developed by evaluation and "optimization" of data from the primary literature. Based on proper thermodynamic models for every phase, all available thermodynamic and phase equilibrium data for a system are evaluated simultaneously in order to obtain one set of model equations for the Gibbs energies of all phases as functions of temperature and composition. In such an "optimization", all data are rendered self‑consistent, discrepancies in the data can often be resolved, and the data can be properly interpolated and extrapolated. In particular, properties of multicomponent solutions can usually be estimated with good accuracy from the optimized model parameters of their binary and ternary sub‑systems. The resulting databases of model parameters can be used for calculating phase equilibria and thermodynamic properties using the FactSage Gibbs energy minimization software.

FactSage accesses both "solution" databases ( .sln, or .sdc files (formerly .sda, .sdb and .dat files)) and "pure compound" databases ( .cdb files). The former contain the optimized parameters for solution phases. The latter contain the properties of stoichiometric compounds, either obtained from optimizations or taken from standard compilations.

The documentation file you are now reading gives a general overview of the use of databases with FactSage 7.0.

Extensive documentation on each individual database can be obtained by clicking on Database Documentation ® database name on the FactSage main menu.

1.2 References

A list of literature references can be found by clicking on General -> List of References or Documentation -> List of References. This contains general references on FactSage, references on thermodynamic and other models, references on the optimizations for the FACT databases, references on applications of FactSage, and references to relevant book chapters and general articles on thermodynamics.

2.0 GENERAL COMPOUND DATABASES

2.1 The FactPS (FS53Base.cdb) general compound database

This database contains data for approximately 5000 compounds. It contains selected data for thousands of compounds taken from standard compilations as well as most of the data for those compounds which have been evaluated/optimized to be thermodynamically consistent with the FToxid, FTsalt, FThall, . . . etc. solution databases. That is, for these compounds, the data for the solid and liquid phases in the FactPS database and in the FToxid, FTsalt, FThall, . . .etc. compound databases are identical. (Data for the gaseous phase are generally found only in the FactPS database.) In a few cases, the data for a phase in the FactPS database may differ somewhat from that in the FToxid, FTsalt, FThall, . . . etc. compound databases. In the event of duplication you should preferentially select the species from the FToxid, FTsalt, FThall, . . . etc. database as described in section 3.1.1 (Never simultaneously select the same species from more than one compound database.)

For most compounds in FactPS care has been taken to ensure that the Cp expressions for a phase extrapolate in a reasonable fashion outside the temperature range of stability of that phase. If data are available in a metastable temperature region, then they have generally been used. If data in a metastable region are not available, then the Cp equation from the stable region may still be extrapolated for some distance outside the stable range provided that such an extrapolation seems reasonable. However, if such an extrapolation would result in an enthalpy or entropy of a metastable phase transformation becoming unreasonably small or large, then the Cp expression for the metastable phase has been set equal to that of the stable phase in that temperature region. At temperatures above the upper temperature limit of the highest Cp range for a phase, the Cp is set to be constant and equal to its value at that upper temperature limit.

2.2 SGPS (SGPSBase.cdb) – the SGTE pure substances database.

This is the pure compound database for over 3750 compounds compiled by the SGTE groups. In general, these data have not been optimized to be necessarily thermodynamically consistent with the SGTE solution databases.

We have found that extrapolation of the SGTE Cp equations for a phase outside of its temperature range of stability can frequently lead to errors such as a phase spuriously becoming stable at a high temperature. Consequently, we have set the Cp expression for every solid and liquid phase (S1, S2,..., L) at any temperature equal to that of the most stable solid or liquid phase at that temperature. Consequently, enthalpies and entropies of transformation between all solid and liquid phases will always be calculated as being temperature independent. (For the gaseous phase, the SGTE Cp expression is extrapolated.)

2.3 The FTdemo pure compound (FS50Base.cdb) and solution (FS50soln.sdc) databases:

The worked examples (“slide show examples”) which are included with the Reaction, Predom, Equilib and Phase Diagram modules generally use the FTdemo demonstration databases. These are the former FACT databases from FactSage 5.0. In this way, the species, phase selection and thermodynamic data presented in the Slide Show documentation will not change when FTdemo data are employed.

The FTdemo databases should only be used for the slide shows. Since the results can be imprecise and even completely wrong, you must never publish results that use FTdemo data.

3.0 CORRESPONDING SOLUTION AND COMPOUND DATABASES

3.1 Corresponding solution and compound databases:

There are several FactSage-accessible solution databases such as FToxid, FTsalt, FTlite,

FSstel, SGnobl, etc. (see “Summary of Databases” for a complete listing), each containing data for a group of systems (oxides, salts, light metals, steel, noble metals, etc.)

For each of these solution databases, there is a corresponding coupled pure compound database which contains data for all stoichiometric solid compounds which have been optimized to be thermodynamically consistent with the data in the corresponding solution database. If you select a solution from, for example, the FToxid solution database, and a compound from the corresponding coupled FToxid compound database, you are assured of thermodynamic consistency because the two data sets were obtained by simultaneous evaluation/optimization.

3.1.1 Recommended procedure for species selection

Therefore, the recommended procedure for species selection with the Equilib or Phase Diagram modules is as follows. Let us say for example that you want to calculate an equilibrium involving solid stoichiometric oxides, solid and liquid oxide solutions, and a gas phase.

- Select the solution phases from the FToxid solution database.

- Select the solid stoichiometric compounds preferentially from the corresponding FToxid compound database; that is, if the same compound is found in both the FToxid compound database and the general FactPS compound database, select the one in the FToxid database. If a solid compound is found in the FactPS database and not in the FToxid compound database you may, of course, select it as well. However, you will be aware that its properties have not been optimized to be thermodynamically consistent with the solution data.

- Finally, gaseous species should be selected from the FactPS general compound database since, except in a very few cases, the other compound databases do not contain any data for gases.

In order to assist users in selecting compound species, a new feature was added in FactSage 6.4. When two or more databases are connected, the same species may appear in more than one database. In such cases, a species should generally only be selected from one database.

Otherwise, conflicts will probably occur. In order to assist users in deciding which species to exclude, the FactSage developers have assigned automatic priorities. When you initially click on “pure solids”, “pure liquids” or “gas” in the Equilib and Phase Diagram modules you may see that several species marked with an “X” have not been selected. That is, they have been excluded by default because of probable conflicts between databases. The FactSage developers suggest that these species not be selected for this particular calculation. For further information see slide show à Equilib regular features à Section 19.

3.1.2 Database naming convention

Note that the "53" in a database name (e.g. FS53base.cdb) indicates that it was released for the first time with FactSage 5.3. Most of the databases released with FactSage 5.4, 5.5 and 6.0 have been updated. However, they retain the "53" designation.

4.0 THE FACTSAGE ELEM COMPOUND DATABASE

The ELEM database contains standard state data for all the elements taken from the FactPS compound database. This database is consulted internally by the FactSage modules in order to obtain reference states for the calculations. You do not need to activate this database during any calculations, however you must not delete it from your computer. The modules EQUILIB and PHASE DIAGRAM always require standard state data for the elements, even elements that may not be involved in the calculation. With FactSage 5.3 and earlier versions you may get the following error message: "X - Data missing for this standard state element." If you receive such a message, go to the reactants window of EQUILIB or PHASE DIAGRAM, click on Data search -> Databases, and then include the ELEM database in your data search. It is not necessary to actually select any elements from ELEM in your species selection.

5.0 DOCUMENTATION FOR ASSISTANCE WITH SPECIES
AND PHASE SELECTION

Several features of FactSage are designed to aid users in making a proper selection of solution and compound species when using the Equilib or Phase Diagram modules. One such feature is the use of corresponding solution and compound databases as described in Section 3.1 and 3.1.1. Another is the nomenclature for approved solution subsets as described in Section 6.

In addition, several types of database documentation can be obtained from the main FactSage menu by clicking on Documentation ® name of database:

5.1 General Description of a database

In the main FactSage menu, click on Documentation ® name of database ® General Description to obtain an overview of the contents of the database, the systems, components and phases, composition and temperature limits of applicability, estimates of accuracy, etc.

5.2 List of optimized systems and calculated binary phase diagrams

In the main FactSage menu, click on Documentation ® name of database ® List of optimized systems and calculated binary phase diagrams.

This will open a file with tables summarizing the contents of the database in terms of the assessed and optimized systems and phases it contains. These tables assist in species selection for a calculation by providing:

- a list of all the unary, binary ternary and quaternary systems which have been assessed (i.e. for which assessed parameters are in the database)

- a list of all assessed phases in each of the systems

- assistance with phase selection

- reference numbers (see Section 1.2) for published articles giving detailed descriptions of the optimizations for most systems, showing agreement with experimental data, etc.

Furthermore, phase diagrams have been calculated for all the binary, and some ternary, systems using the assessed parameters contained in the database. The diagram for a particular binary system can be viewed by clicking on the name of the system in the table. The diagrams contain the names of the stable phases in each system and thus provide guidance in phase selection for calculations in higher‑order systems. (Alternatively, the same diagrams can be displayed by following the procedure described in Section 5.3)

By referring to these tables and phase diagrams, the user will be able to determine whether proposed calculations for a particular higher‑order system will be based on a complete set of assessed binary and ternary parameters (at best) or summation of binary parameters only (at worst). Clearly the latter case, or use of incompletely assessed data sets, can lead to incorrect or unreliable results. In a binary system, if no assessed mixing parameters are available for a particular phase, the phase will be treated as ideal. Correspondingly, the properties of a ternary or higher‑order phase will be calculated applying the appropriate models used in the database. This procedure may give useable results if the alloy compositions in question are close to a pure component or to a binary edge for which assessed data are available. However, results of calculations for other composition ranges should be treated with great caution.

5.3 Phase Diagrams

In the main FactSage menu, click on Documentation ® name of database ® Phase diagrams. A list will appear of phase diagrams which have been calculated for all binary, and some ternary, systems using the assessed parameters contained in the database. The diagram for a particular binary system can be viewed by clicking on its name. (Alternatively, the same diagrams can be displayed by following the procedure described in Section 5.2).

5.3.1 Calculating documented phase diagrams with the PhaseDiagram module:

You may also use the PhaseDiagram module to calculate any diagram from the documentation. On the menu window of the Phase Diagram module, click on the yellow file folder icon and then click on the yellow file folder icon again. Select the database of interest and then click on the name of the system whose phase diagram you wish to calculate. This will automatically set up the input for that diagram, with the correct species selection in place.

5.4 List of compounds and solutions

In the main FactSage menu, click on Documentation ® name of database ® List of compounds and solutions to obtain a listing and a brief description of all compounds in the compound database and of all solution phases in the corresponding solution database.

5.5 Description of solution phases

When executing the Equilib or PhaseDiagram modules, on the main menu window, right click on the name of the solution phase and then click on more information. Detailed information on this solution phase will then be displayed. This information includes the phase components, limits of applicability, compatibility with other solutions and compounds, conditions under which this phase should or should not be selected, whether the immiscibility ("I") option needs to be used, etc.

The entire file containing these detailed descriptions of all the phases in the solution databases can be displayed from the main FactSage menu under Documentation ® name of database ® Description of solutions.

6.0 THE MEANING OF "SOLUTIONA, SOLUTIONB, SOLUTIONC, . . . ., SOLUTION?"

Many solutions in the FACT (FTxxxx) solution databases contain a large number of components, but not all binary and ternary sub‑systems have been assessed and optimized; sub‑systems which have not been assessed and optimized are assumed ideal or are approximated. Properties of multicomponent solutions are estimated from the assessed binary and ternary parameters by means of the solution models. In some cases these assumptions, approximations and estimates are adequate, but in other cases, caution should be exercised. Consequently, for certain solution phases, the databases contain approved lists of those components which, if grouped together as a multicomponent solution, can be expected to result in reasonable calculations. This applies mainly to the FToxid and FTsalt databases.

As an example, the molten salt solution FTsalt‑SALT contains a large number of components. The components in the group (LiCl-NaCl-KCl-MgCl₂-CaCl₂-MnCl₂-FeCl₂-FeCl₃-CoCl₂-NiCl₂) have been assessed together, and so calculations involving this solution (or any sub‑system thereof) are approved. This is the solution "FTsalt‑SALTB". Also, the components in the group (LiCl-NaCl-KCl-RbCl-CsCl-MgCl₂-CaCl₂-SrCl₂-BaCl₂) have been assessed together, and this is the approved solution "FTsalt-SALTD. There are also other approved component groupings (FTsalt‑SALTC, . . . . , FTsalt-SALTH). Finally, FTsalt‑SALT? contains all the components in FTsalt‑SALT. Suppose that you are performing a calculation involving the reactants NaCl-KCl-SrCl₂-CoCl₂. When you use the Equilib or PhaseDiagram modules you will be given the choice of selecting FTsalt-SALTB (which will contain NaCl-KCl-CoCl₂ but not SrCl₂), or FTsalt-SALTD (which will contain NaCl-KCl-SrCl₂ but not CoCl₂), or FTsalt-SALT? which will contain all four chlorides. (Right click on the phase name in the menu window of the Equilib or Phase Diagram module to see the list of components in each group which are relevant to the current calculation.) You have now been alerted to the fact that no assessments have been made for solutions containing SrCl₂ and CoCl₂ simultaneously. If you select SALTB, then the calculations will give SrCl₂as insoluble in the molten salt solution. If you select SALTD, CoCl₂ will be calculated to be immiscible. You can now still proceed, if you wish, and perform calculations involving the entire NaCl-KCl-SrCl₂-CoCl₂solution, by clicking on FTsalt-SALT? but you will have been made aware that this is not an approved group of components and that substantial inaccuracies in the calculations may result.

6.1 How this is differenet in the FTdemo slide show

Continuing with the preceding example, with FactSage versions 5.3 and higher, "FTsalt-SALTB" is always the group (LiCl-NaCl-KCl-MgCl₂-CaCl₂-MnCl₂-FeCl₂-FeCl₃-CoCl₂-NiCl₂), "FTsalt-SALTD" is always the group (LiCl-NaCl-KCl-RbCl-CsCl-MgCl₂-CaCl₂-SrCl₂-BaCl₂), etc. Formerly, with FactSage 5.2 (and earlier versions) however, the first approved group found to contain components relevant to a given calculation was always called "SALTA", the second was always "SALTB", and so on in alphabetical order. So in the above example, with FactSage 5.2 the NaCl-KCl-CoCl₂ solution would have been "SALTA" and the NaCl-KCl-SrCl₂ solution would have been “SALTB”. However, the same solutions might well have been assigned other letters in other calculations with different reactants.

Note: If you use the FTdemo FactSage slide show demonstration databases (see Section 2.3 above), then the old system will be in effect even with FactSage versions 5.3 and higher since the slide show examples generally use the former FACT (FT50) compound and solution databases.