Thermodynamic data databases

Raevsky and co-workers have collected a large database of thermodynamic data related to hydrogen bonding with which they have developed the HYBOT program... 

Does the thermodynamic dataset contain the species and minerals likely to be important in the study A set of thermodynamic data, especially one intended to span a range of temperatures, is by necessity a balance between completeness and accuracy. The modeler is responsible for assuring that the database includes the predominant species and important minerals in the problem of interest. 

The choice of a given database as source of auxiliary values may not be straightforward, even for a thermochemist. Consistency is a very important criterion, but factors such as the publication year, the assignment of an uncertainty to each value, and even the scientific reputation of the authors or the origin of the database matter. For instance, it would not be sensible to use the old NBS Circular 500 [22] when the NBS Tables of Chemical Thermodynamic Properties [17], published in 1982, is available. If we need a value for the standard enthalpy of formation of an organic compound, such as ethanol, we will probably prefer Pedley s Thermodynamic Data and Structures of Organic Compounds [15], published in 1994, which reports the error bars. Finally, if we are looking for the standard enthalpy of formation of any particular substance, we should first check whether it is included in CODATA Key Values for Thermodynamics [16] or in the very recent Active Thermochemical Tables [23,24],... 

Thermo-Calc (Sundman et al. 1985, Andersson et al. 2002). ft features a wide spectrum of thermodynamic models, databases and modules making it possible to perform calculations on most problems involving phase equilibria (phase transformation, stable and metastable equilibria, etc.). The calculations are performed using databases produced by an expert evaluation of experimental data. There are thermodynamic databases available for many different systems and applications. 

DATABASES (thermodynamic and diffusion). The calculations require a database for the material systems of interest. For the commercially important materials, databases have been developed by teams of experts critically assessing all experimental phase equilibria and thermodynamic data and, for the complex systems relevant for applications, by extrapolating from binary, ternary and quaternary subsystems. 

CHEMThermo Automatic Comparison of Thermodynamic Data for Species in Detailed Chemical Kinetic Modeling, Simmie, J. M Rolland, S. and Ryder, E. Int. J. Chem. Kinet. 37(6), 341-345, (2005). CHEMThermo analyses the differences between two thermodynamic databases in CHEMKIN format, calculates the specific heat (Cp), the enthalpy (IP), and the entropy CS °) of a species at any given temperature, and compares the values of Cp, II", S" at three different temperatures, for the species in common. Refer to the website http //www.nuigalway.ie/chem/c3/software.htm for more information. 

Data for other substances can be obtained from the following critical compilations and online in the NIST Chemistry WebBook at http //www.webbook.nist.gov/ chemistry/ or from the NIST-TRC Databases available on disk. (Information can be found at http //www.nist.gov/srd/thermo.htm, or at http //srdata.nist.gov/ gateway/gateway keyword = thermodynamics.) An exhaustive list of earlier sources of tabulated thermochemical data can be found in Volume 1 of Chemical Thermodynamics, A Specialist Periodical Report [2]. A useful list of websites containing thermodynamic data is available at http //tigger.uic.edu/ mansoori/ Thermodynamic.Data. and.Property.html. 

Table 5.69 lists thermal expansion and compressibility factors for some Si02 polymorphs, according to the databases of Saxena et al. (1993) and Holland and Powell (1990). Table 5.70 lists thermodynamic data for the various Si02 polymorphs according to various sources. 

STABCAL was also used to construct pE-pH stability fields for chloropyromorphite, hinsdalite, plumbogummite, tricadmium diphosphate, tricopper diphosphate, and hopeite (Fig. 7). These diagrams allow for estimation of stability with respect to pH and to the presence of insoluble sulphides. The NBS thermodynamic database (Wagman et al. 1982) was used as a source of thermodynamic data. The total concentrations chosen for each metal were selected to produce a stability region for the metal phosphate solid. In some cases, this was a very low total concentration (e.g., CTPb =1 x 10 10 M for Pb). In other cases, the total metals concentration was high (e.g., C r.cd— 1 x 10 3 M for Cd). The modelling exercise used typical equilibrium concentrations for MSW bottom ash leachates as shown in Table 2. 

Kulik, D. A. 2002. Minimising uncertainty induced by temperature extrapolations of thermodynamic data A pragmatic view on the integration of thermodynamic databases into geochemical computer codes. Proceedings of the Workshop on The Use of Thermodynamic Databases in Performance Assessment , 29-30 May 2001, Barcelona, Spain. Organisation for Economic Cooperation and Development OECD, Paris, France, 125-137. 

For a problem involving surface chemistry, the next step is to execute the Surface Chemkin Interpreter, which reads the user s symbolic description of the surface-reaction mechanism. Required thermodynamic data can come from the same Thermodynamic Database used by Chemkin or from a separate Thermodynamic Database compiled for surface species. Both Interpreters provide the capability to add to or override the data in the database by user input in the reaction description. The Surface Chemkin Interpreter extracts all needed information about gas-phase species from the Chemkin Linking File. (Thus the Chemkin Interpreter must be executed before the Surface Chemkin Interpreter.) Like the Chemkin Interpreter, the Surface Chemkin Interpreter also provides a printed output and a Linking File. Again, the Surface Linking File is read by an initialization subroutine in the Surface Subroutine Library that makes the surface-reaction mechanism information available to all other subroutines in the Library. 

Thermodynamic data at 298.15 K were mostly taken from Wagman et al.3 High temperature data for the above-mentioned three sulfites were taken from the HSC database referred to in Chapter 1.1. No thermodynamic data for oxides are included, since they were already given in Chapter 2, and sulfates, which may also be decomposition products, are described in Chapter 4. Therefore, when only minimal data are available, they are given in the text rather than in individual tables. 

Table 21 shows a variety of thermodynamic data collections and the elements considered. The thermodynamic data are usually not available in a current database format (exception CHEMVAL 6 as dBASE file) but in a form which is needed for the specific program. To use thermodynamic data in PHREEQC which are applicable e g. for EQ 3/6 or PHREEQC, they have to be converted into the respective format (e g. PHREEQC) using a transfer program. 

However, the most common sources of different results are both based on the approach used for the calculation of the activity coefficient (chapter 1.1.2.6) and the thermodynamic data sets themselves (chapter 2.1.4), which provide the respective program with the fundamental geochemical information of each single species. The thermodynamic databases available partly use severely differing data with different solubility products, different species, minerals and reaction equations. Nordstrom et al (1979, 1990), Nordstrom Munoz (1994), Nordstrom (1996, 2004) discuss this inconsistency of thermodynamic datasets in detail. For some species, for which stability constants have been published, not even the existence of the respective species has been proved doubtless, as can been shown in the following example. 

The data sets WATEQ4F.dat, MINTEQ.dat, PHREEQC.dat and LLNL.dat are automatically installed with the program PHREEQC and can be chosen from the menu item Calculations/File under Database File. The internal structure of these thermodynamic data sets has already been explained in great detail in chapter... 

These programs are able to model the geological systems soil/rock-aqueous solution systems that is the concentration and distribution of the thermodynamically stable species can be determined based on the total concentrations of the components and the parameters just mentioned. In addition, the programs can also be used to estimate thermodynamic equilibrium constants and/or surface parameters from the concentrations of the species determined through experiments. Thermodynamic equilibrium constants can be found in tables (Pourbaix 1966) or databases (e.g., Common Thermodynamic Database Project, CHESS, MINTEQ, Visual MINTEQ, NEA Thermodynamical Data Base Project (TDB), JESS, Thermo-Calc Databases). Some programs (e.g., NETPATH, PHREEQC) also consider the flowing parameters. 

The general methodology used can be described as follows. The user sets up the problem by specifying the type of calculation to be made (e.g. isotherm, isopleth, or liquidus projection) and then selects the database from which the thermodynamic data will be imported. The system components are defined, as well as the phases that are present and the temperature, pressure, and composition ranges over which to make the equilibrium calculations. All of this is accomplished via the user interface. 

Databases with assessed thermodynamic data for hundreds of substances are available, including alloys, semiconductors, geochemical compounds (silicates and other main-group oxides), aqueous solutions, and molten salts. The bulk of the commercially available databases are on metallurgical systems since the CALPHAD method finds ready applicability in the fields of metals processing and alloy development. 

Because the author was unable to review the proofs to the second edition, numerous printing errors appeared in that edition. Apologies are due for the inconveniences caused. Much care has been exercised in the printing of this edition. SI units are used where appropriate throughout, particularly for thermodynamic data so that these data are now consistent with the JANAF tables in the appendix. In some instances where certain cgs databases have not been updated and where cgs units are so ingrained that SI may have proved an inconvenience, cgs units have prevailed. The table of conversion factors in the appendix should reduce any inconveniences. 

Graphics-based Hiickel molecular orbital calculator of energies and orbitals of TT electrons. EnzymeKinetics for fitting Michaelis—Menten kinetics parameters. ESP (Experimental Section Processor) for organizing synthetic procedures in publication format. LabSystant for evaluating quantitative lab data. Diatomic Molecular Motion and Mechanics. PC-Mendeleev for studying periodic table. SynTree for creating database of reactions. TAPP (Thermodynamic and Physical Properties) database with physical and thermodynamic data on more than 10,000 compounds. PCs and Macintosh. 

Tel. 301-975-2208, fax 301-926-0416, e-mail rdj3 enh.nist.gov Thermodynamic data for almost 5000 gas phase compounds. Estimations of structures drawn into program using Benson s additivity rules. IVTAN-TFIERMO database with enthalpies of formation and other thermodynamic properties for 2300 substances. PCs. 

Caffrey, M. Lipidat a Database of Thermodynamic Data and Associated Information on Lipid Mesomorphic and Polymorphic Transitions CRC Press Inc. Boca Raton, PL, 1993 305. 

---