From: Validation of hydrogeochemical databases for problems in deep geothermal energy
Code | PHREEQC | ChemApp | ||
---|---|---|---|---|
Parameter file | phreeqc.dat | llnl.dat | pitzer.dat | slop16.dat |
Source of thermodynamic data | Unknown | Mainly: slop | Unknown | slop16 |
Activity model | Extended Debye–Hückel equation | Pitzer equations | Davies equation | |
Approx. ionic strength limits of the activity model \(\left( {\mathrm {mol}}/{\hbox {kg}}\right)\) | 0.1–3^{a} | 0.1–3^{a} | 6^{a} | 0.1–0.5^{a} |
Pressure dependence | HKFmoRR | None | HKFmoRR | HKF |
Temperature dependence | Fitted polynomial equation or two-term extrapolation [cf. Eqs. (1) and (2)] | HKF |