> Having started to use the new version of PHREEQC (version 2) in an inverse modelling mode, I tried running old models (run on version 1.03 PHREEQCi) to check the feasible models were the same. Unfortunately I find that the number of feasible models produced in version 2 is always less. It looks like some of the reactions pass your 1e-7 tolerance in one version, but not the other. If you lower that tolerance (default is around 1e-10, I think), then the two versions give the same number of minimal models. I think the differences you are seeing are related to handling small numbers. The redox reactions that account for the differences are on the order of 1e-7. There may have been some changes in the way the equations were scaled between the two versions that accounts for the difference. If you are worried about the differences, which are on the order of 1e-7, then you need to use a smaller tolerance (this is not the uncertainty). If you do use a smaller tolerance, it looks like the two versions are consistent. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225
Please note that some U.S. Geological Survey (USGS) information accessed through this page may be preliminary in nature and presented prior to final review and approval by the Director of the USGS. This information is provided with the understanding that it is not guaranteed to be correct or complete and conclusions drawn from such information are the sole responsibility of the user.
Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.
The URL of this page is:
Last modified: $Date: 2005-09-13 21:04:21 -0600 (Tue, 13 Sep 2005) $
Visitor number 1230 since Jan 22, 1998.