Solid-solution modelling with GWB

[steve crowley]

I have tried modelling siderite-magnesite solid solutions using the community version of GWB. I decided to check the properties of various carbonates used in model calculations, including calculation of molar volumes for pure carbonate phases from unit cell parameters. I obtained generally good agreement with GWB properties listed for calcite, magnesite and rhodochrosite, but found a large difference between the GWB value (28.630 cm3/mol) and a value calculated from unit cell data (29.376 cm3/mol) for siderite.

Also, I don't appear to be able to access the continuous SS modelling option in the community version.

Would anyone care to comment? 

[Jia Wang]

Hello,

The default thermo dataset thermo.tdat was originally published by Lawrence Livermore National Laboratory. You can find the information regarding the publication at the top of the thermo dataset or in the Headers Pane if you open it in TEdit. Please contact the corresponding author regarding compilation method and discrepancies.

If you like to edit the dataset to use the value you calculated, you can use TEdit or simple text editor to do so.

Could you describe what you have done so far in setting up your siderite-magnesite solid solution? If you are using SpecE8 to perform chemical speciation calculations, make sure that the "type" set for your solid solution is "continuous", which should be the default when you are configuring it in SpecE8. You may also add solid solutions to a thermo dataset and load it in along with the rest of your thermodynamic parameters. Note that solid solutions will be available only in discrete mode in Act2 and Tact.

For more information on solid solution configuration, you can refer to section 2.5 of the GWB Essentials User's Guide.

Best regards,
Jia Wang
Aqueous Solutions LLC