Search the Community

Hello all, I am attempting to model alteration mineral formation from an ultramafic composition, but cannot get a solution that converges. I have tried changing the parameters in the Config -> Iteration and Config -> Stepping settings, but it still won't converge. The error I get is: N-R didn't converge after 999 its., maximum residual = 2.46e-15, Xi = 0.0000 Largest residual(s): Resid Resid/Totmol Cbasis --------------------------------------------------------- Fe++ -4.405e-20 2.46e-15 1.074e-12 --------------------------------------------------------- My epsilon value is also 1e-11, so not sure why these lesser residuals count as not converging. This is for a planetary application, so the actual fluid chemistry is not constrained. Can someone please give me some advice on what changes should be made to the Basis fluid chemistry to make the solution converge? Or are there any "standard" Basis fluid chemistry packages that I could use to attempt to achieve solution convergence? The current React model is attached. Thank you in advance for your help and advice, it is much appreciated. All the best, Jesse Chassigny_Freshstart_USE_AllMins.rea

Good day! My name is Justin Whitaker and I am a 4th year Honour's student at the University of Ottawa as part of the Fortin lab group. This is my first post to this forum and I thank you for reading my post - and hopefully fielding it as well! At the present time, I am currently conducting some Geochemistry work as part of my cross-disciplinary Honour's work but, as a biomedical and medicinal chemist by training, I have not had any formal training in programs such as PHREEQC. From my research online, it is clear that this may be an area I can get an answer to my problem! I believe my situation may be a simple one to comment on and fix. As a complete novice to the program I have not written any specific code to review. However, I understand how to enter and define basic solutions from my online research. My colleagues also only have a basic understanding of PHREEQC as it is related to geochemistry and suggested that I get into contact with leading experts knowledgeable in the field of geochemistry. So I am here! At present, I am attempting to model a media solution containing the following compounds: (1) Trizma Base (10g/L) (2) Urea (0.125M) (3) (NH4)2SO4 (0.005M) (4) Yeast Cell Autolysate (10g/L) (5) Trace Metal Addition (Calcium, Magnesium, Zinc, Copper, Iron, Nickel) pH = 8.0 Temperature = 28 degrees celcius My question is: How I would input and model compounds such as Trizma base (2-Amino-2-(hydroxymethyl)-1,3-propanediol), Urea ( (NH3)2CO) as well as amino acids (the Yeast Cell Autolysate being a heterogeneous of phosphate, trace vitamins and surplus amino acid content) into the program? Most especially the amino acids with their reactive ammonium and carboxylic moieties! The penultimate goal is to determine if any of the trace metals I am adding into the media will precipitate, thermodynamically, at the concentrations I intend to add to the media solution (0.01 - 0.20uM). The addition of the trace metals is to see their effect on the growth of a bacterial strain I am working with and if the incorporation of the metals (tested one at a time and in different bacterial flasks and batches) affects the activity of a special enzyme (urease). Thank you for your time and effort in fielding this question, if possible! I hope that the parameters are clear and that an answer could be fielded with little inconvenience or strain on anyone's schedule. Please know that anyone's time and effort are certainly most appreciated! With kindest regards, Justin Whitaker