HSC issues

[francesco77]

Hi,
I'm experiencing some issues using HSC-equilibrium-calculations:

I attach some plots to show the different behaviours of several compounds from a range of computations I have run.
All my models are over a temperature range T=50K-1850K for specific pressures (P=10^-5 or 10^-3).
I then:

1) change the number of steps used over the T range (fig.1 uses 50 steps --- fig.2 uses150 steps -- both with P=10^-3)

fig1



fig2



2) change dT with the same number of steps. (fig.3 50K-1850K using 30 steps--- fig.4 1000K-1850K using 150 steps -- both with P=10^-5)

fig3



fig4




I'm using a complex model, with several activity coefficient equations for a range of species and phases.

Sometimes I notice very irregular composition plots: there are some points (in temperature) that are not calculated, several spikes and when I choose different numbers of temperature steps for the same dataset very different results can be seen.
E.g. Al2O3 is present in one computation (fig.2) while not in the other one (fig.1).

Has any one experienced similar types of problems? Can anyone suggest what is going on and/or how we can solve this problem?


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Sometimes HSC also return me this error:

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Info Error

Error 20002:
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This seems to happen "randomly".
e.g.:
-I change the values of steps, T or P. I save the file, click on "calculate" in the Gibbs-Equilibrium-Solver and software returns this error.
The file becomes corrupted and I have to use my back-up-file in order to recover my work.
- Sometime when I change an equation for the activity coefficients, the previously saved the file doesn't work anymore.
-Sometimes files that work don't work anymore if I simply close and rerun HSC.


We made a repair-installation and a new installation, but these operations didn't solve our problems.
Do you have some informations about this error?

Thank you.

Francesco

[Eltee]

"Sometimes I notice very irregular composition plots: there are some points (in temperature) that are not calculated, several spikes and when I choose different numbers of temperature steps for the same dataset very different results can be seen."
"Has any one experienced similar types of problems? Can anyone suggest what is going on and/or how we can solve this problem?"

I've seen this sort of behavior (single point deviation from general trends in adjacent points; missing points), but can only speculate on the specific cause here. Two possibilities are:

1. Convergence criteria too large for the quantity of material present in the calculation. A possible solution is to increase the quantities of material present by, say 1000 or 1,000,000, then reduce all quantities by the same factor after calculation

2. Linear dependence of certain elements. This is a little difficult to explain briefly, but most of the degrees of freedom in the equilibrium calculation are "quantity of element 'X.'" In many problems, within the set of species provided, certain elements are always found in a distinct ratio to another element (e.g., if all carbon and oxygen were present only in "CO3", then the quantity of C and O cannot be independently varied), yet the calculation scheme attempts to calculate them independently. There is no convenient provision to force HSC to treat functional groups like CO3 as immutable entities. (Linear dependence of element quantities can be more subtle than this example). When this happens, the calculation scheme often has trouble reaching a solution. This can be "cured" by adding, a tiny quantity of some other starting species containing these elements in a different ratio. That will bump the calculation off the "stoichiometric boundary" and may resolve the issue.

[francesco77]

HI Eltee, thank you
I will use your suggestions and I will report results