[OLD] Problems w/ Ce in the expanded thermo dat

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From: Rainer Newberry

Subject: Problems w/ Ce in the expanded thermo database

Does anyone know what's wrong with or how to fix the Ce entries in the expanded thermo database in gwb? Data for Ce4+, Ce3+, and Ce2+ species are given for 25oC, but when trying to create diagrams using Act2 or Tact, all that shows up is 'Ce++'. At other temperatures (e.g., 24C or 26C) the Ce+++ species plot up nicely, but (due to lack of data) none of the other oxidation states of Ce. If one turns on 'extrapolate' , again all that shows up is 'Ce++'.

 

From: Craig Bethke

Subject: Re: problems w/ Ce in the expanded thermo database

Well, my cerium chemistry is a little rusty, but I notice the log K for the Ce+++/Ce++ redox couple corresponds to a Nerst Eh of more than 6 volts. So I think you can safely assume that this value

is in error. The solution (assuming you don't care about the divalent form) is to decouple the Ce+++/Ce++ reaction. Alternatively, you can check the cited source: Spahiu, K., and Bruno, J., 1995, A selected thermodynamic database for REE to be used in HLNW performance assessment exercises: SKB Tech. Rep. 95-35, 80 p.

 

From: Rainer Newberry

Subject: Ce update (a topic obviously near the top of everyone's concerns)

As Craig Bethke pointed out, the data for Ce++ in the expanded thermo data set is bogus, and as he pointed out, the way to get around it is to 'decouple Ce++'. It would be useful to keep track of any other problematic data as people encounter them. Has anyone else experienced such?

 

From: Rainer Newberry

Subject: Ce update

The data for Ce++ in the expanded thermo data set is bogus, and as he pointed out, the way to get around it is to 'decouple Ce++'. It would be useful to keep track of any other problematic data as people encounter them. Has anyone else experienced such?