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Re: convergence problem

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 Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

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