Jump to content
Geochemist's Workbench Support Forum

Reaching Max Residual with Calcite


Recommended Posts

I was wondering if I could get some help with one of my models. I am recreating a soil profile with various minerals and measuring the rate of carbon consumption. The model works and runs perfectly until I add "Kinetic Calcite" into my reactants and then the simulation only gets a minute in before coming up with the message "Newton-Raphson didn't converge after 999 iterations, max residual =    4.27e-07, Xi = 0.0031  / Newton failed at node 0". I was wondering if one of your team could get a better understanding about why I run into this problem. I have attached my input file below.

Weathering Soil Test Broken.x1t

Link to post
Share on other sites

Hello Alex,

I took a quick look at your script and noticed that you have set a really high rate constant for kinetic calcite relative to all the other minerals in your system. To investigate error, I shortened the run time on your simulation to 1 day and looked at mineral dissolution rates during the simulation. Because of the high rate constant for calcite, you have high reaction rates adjacent to zero rates, in a moving front as the model progresses. To see this, plot the x-position on the x-axis and dissolution rate of calcite on the y-axis. Since the rate constant for calcite is many orders of magnitude higher than other minerals, it might be better to consider calcite using the equilibrium approach. If you want to continue using a kinetic rate law for calcite precipitation/dissolution, you should reconsider the rate constant that you are using. 
 
I also noticed that you have set a nucleus density for tridymite, kaolinite, and illite. This is only necessary if the mineral you are setting up a kinetic rate law for does not exist in the system. In your case, you do not need them. 
 
Hope this helps,
Jia Wang
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...