Hello Henning, I took a look at your convergence problem. I think the problem is in the definition of two copper polysulfide species. It should be -mass_balance Cu(1)(S(-2)4)2 and Cu(1)S(-2)4S(-2)5. As it is currently defined, these species are going into the Cu(2) mole balance, but adjusting the Cu+2 activity makes no difference in their concentration because Cu+ is in the mass action equation. Changing the -mass_balance puts the species in the Cu(1) mass balance. I'm not fond of polysulfide species anyway; they are metastable, so there is a question of whether they should be used in a model, and they tend to cause convergence problems. Hope this helps. Good to hear from you and take care, David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225
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