Databases

[EMH121]

LLNL DB appears to have has a five term analytic expression for the temperature dependence of logK for a defined chemical reaction. PHREEQC DB has 6 terms in the form logK = a + b*x + c/x +d*log10(x) + e/(x^2) + f*(x^2), where x= t in oK. Can you please provide the 5 term equation format for the LLNL DB? Thanks in advance.

[dlparkhurst]

The analytical expressions are the same for all databases. If only five parameters are used, it is the first five parameters of the expression and the sixth is zero.

[EMH121]

Thank you! I briefly looked at the 10 DB options in PHREEQC. Does anyone update the information in these DBs, such as logK, analytic expressions, Vm, etc? For example pKa2(H2S) ~13 is used in all DBs except SIT, although that value has been known to be incorrect for over 30 years. Which is / are the best maintained in PHREEQC? SIT thermodynamic data is referenced.

Is there another entity, such as Geochemists Work Bench, NIST, or any entity, of course including PHREEQC, that continally updates its DB(s)?

[dlparkhurst]

You are more than welcome to continually update databases.

The ones I know about are mostly in the nuclear waste side of things.

ANDRA French National Radioactive Waste Management Agency ThermoChimie  (http://www.thermochimie-tdb.com/) [BRGM, Amphos21 (Spain), Institut de Chimie (University of Poitiers)]

BRGM-Themoddem (http://thermoddem.brgm.fr/)

JAEA, Japan (http://migrationdb.jaea.go.jp)

Nagra-PSI, Switzerland

OECD-NEA (http://www.oecd-nea.org/dbtdb/)

SCK CEN—Belgian Nuclear Research Center (https://www.sckcen.be/)

[EMH121]

Thank you for your reply Dr Parkhurst. Anyone who took on the job of updating the /a DBs would be doing the geological community a great service, but it would be a huge job. Unfortunately, I am not that person because I am not a very good physical chemist, as well as having limited exposure to thermodynamic data. I do plan to contribute the script for my S-species DB to the PHREEQC and GWB communities, but if accepted, it would reside outside of the other DBs unless someone incorporated it within a DB. I would think that other specialists also have contributed and will contribute their DBs.

The GeochemistsWorkBench website, https://www.gwb.com/thermo.php, lists additional DBs. GWB also does not update any DBs, saying that it is a conflict of interest to choose one data set over another.

NIST generates a number of DBs, including one for thermodynamics of organics that is continually updated. They also have one for metal-ligand  stability constants that is now discontinued, free at https://www.nist.gov/srd/nist46.

[dlparkhurst]

I should say that Tony Appelo has been making continuous updates to phreeqc.dat, Amm.dat, and pitzer.dat. The recent updates include fitting CO2 and other gas solubilities, calculating molar volumes and densities, calculating specific conductance, and refining multicomponent (and electro-) diffusion, all to higher temperature and pressures.