Geochemist's Workbench Support Forum

# Newton - Raphson didn't converge after 999 iterations, max residuals = Largest residuals :

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Hello, I am currently trying to run a calculation for a reaction that involves any mole of TiO and H3PO4, at any given temperature and pH. However, after I inputed these into the program, and ran the software, a message popped up that said Newton - Raphson didn't converge. I'm only a freshman student at university, straight of high school, so I don't have much knowledge in chemistry or science in general, but I am currently doing research and needed to use this program! Any help would be appreciated! I also hope you can explain it in a simple matter I can understand, because I tried reading the manual and it left me beyond confused.

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Hello Ashley,

SpecE8 allows you to calculation the chemical speciation in an aqueous fluid given a certain set of chemical constraints and the composition of your fluid. I noticed that you swapped in a large amount of TiO(alpha) into the basis pane. Swapping is typically used to set the fluid in equilibrium with a certain mineral, and the program calculates the concentration dissolved in the fluid.

If this is your first project involving geochemical modeling, you might need to put a little extra work in understanding how each GWB application works before attempting to set up to solve the problem of your own. If you find the GWB Essentials Users Guide confusing, a good place to start may be the Geochemical and Biogeochemical Reaction Modeling textbook. You can check if you have access to this resource through your university library. The text provides a good starting point for geochemical modeling theory and application, with many detailed examples for the GWB.

When it’s time to setup your own problem, you would need to identify which GWB application is suitable for your purpose. If you are simply looking at the aqueous speciation of a fluid, then SpecE8 is sufficient. If your reactions involve mineral precipitation or dissolution, then you would need to use React application.

Hope this helps,
Jia Wang

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Thank u so muuuuch for the help! My reactions do involve mineral precipitation or dissolution. So I will try to use the React application. I'll also take a look at the tutorials.

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