Thermodynamic data

[onat.yakisik]

Hello,

Firstly, i would like to present myself. I am Onat Yakisik and i am a phd student at Pavia University. My topic mainly focuses on 0-D batch geochemical model (simulation of basalt alteration due to interaction with acidic CO2-rich fluids) and 1-D reactive transport model to calibrate with aging experiments. So, i study also on PHREEQC software. My tutor and i made a thermodynamic data which covers from 0-300 bar pressure and from 0 to 300 degrees temperature. Thus, my question is how can i convert this data available in PHREEQC ? Thank you

[dlparkhurst]

I assume your data applies to minerals, in which case you will use the data block PHASES to define the thermodynamic data. To cover the temperature range, you need to develop analytical expressions for the log K of each mineral dissolution reaction. The analytical expression uses up to 6 constants in a multi-term function of temperature. To allow the equilibrium constant to be a function of pressure, you need to enter the molar volume of each mineral.  See the description of input for the keyword PHASES in the manual for details.

Here is an example of a PHASES definition for quartz. The analytical expression will be used for temperature dependence in preference to the log_k and delta_h.

Code: [Select]

Quartz
SiO2 + 2 H2O = H4SiO4
-log_k -3.98
-delta_h  5.990 kcal
-analytic 0.41 0.0 -1309.0
-Vm 22.67