I am trying to develop a consistent thermodynamic database for Al-hydroxides and noticed the following in thermo.com.v8.r6
I am trying to verify that I am using SUPCRT92 correctly by comparing SUPCRT92 output with the thermo.com.v8.r6 database.
This database uses Pokrovskii and Helgeson 1995 (American Journal of Science) for the Al-H2O system.
SUPCRT92 has sprons96.dat which also uses Pokrovskii and Helgeson 1995.
The SUPCRT92 calculated log K values for Gibbsite, Boehmite and Diaspore agree at 25 but disagree at other temperatures to varying degrees (See Table below).
Other minerals are exactly consistent, for example, anorthite. Anyone know why or how these values are different?
Log K values
Gibbiste
Temp thermo.com SUPCRT
25 C 7.756 7.756
300 C -2.4754 -1.368
Boehmite
Temp thermo.com SUPCRT
25 C 7.5642 7.564
300 C -2.7773 -2.705
Diaspore
Temp thermo.com SUPCRT
25 C 7.1603 7.160
300 C -2.8906 -2.865
Anorthite
Temp thermo.com SUPCRT
25 C 26.578 26.578
300 C -2.5408 -2.541
According to the GWB thermo.com.v8.r6 database header, they use supcrt as the "extrapolation algorithm (at least for these phases).