Using aux variables and material properties in DerivativeParsedMaterial

[rnpratoori]

Hello,

I am working on a set of phase-field equations where the energy is defined using polymer volume fraction instead of the regular phase field order parameter c. Although I can rewrite the expression using c, it would make it cumbersome.

Now, to combat this, I have defined an aux variable for polymer volume fraction which is calculated based on c. Can I use this to define the expression for energy using DerivativeParsedMaterial? In this case, what will be the coupled_variable? 'c' or polymer volume fraction?

I also have a material property which is calculated at each quadrature point and used in one of the energy terms and is also dependent on polymer volume fraction. How is it handled in DerivativeParsedMaterial?

[GiudGiud]

Hello

An auxiliary variable can be substituted but I would not recommend it if you are using automatic differentiation (AD) or the Derivatives from the DerivativeParsedMaterial because auxiliary variables do not propagate derivatives (there might be a way with the DerivativeParsedMaterial, definitely not with AD)

So instead I would recommend using an AD material property instead

[GiudGiud]

add to the Material

material_property_names = phi

[rnpratoori]

I was just looking at the options for DerivativeParsedMaterial, should phi not be a additional_derivative_symbols

[GiudGiud]

Unlikely, we only need variables there. When assembling a Jacobian we only need derivatives wrt to variables.

If we needed the derivative of this property with regards to phi, it would be for another object s needs.

[rnpratoori]

I wanted to check the Jacobian with the debugger as you suggested. It gives an error message -

 /home/rnp/Software/MOOSE/projects/moose/python/jacobiandebug/analyzejacobian.py CL_CHNS.i
Traceback (most recent call last):
  File "/home/rnp/Software/MOOSE/projects/moose/python/jacobiandebug/analyzejacobian.py", line 339, in <module>
    executable = findExecutable(options.executable, options.method)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rnp/Software/MOOSE/projects/moose/python/jacobiandebug/analyzejacobian.py", line 82, in findExecutable
    elif shutil.which(executable_option):
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/rnp/Software/miniforge/envs/moose/lib/python3.11/shutil.py", line 1493, in which
    if os.path.dirname(cmd):
       ^^^^^^^^^^^^^^^^^^^^
  File "<frozen posixpath>", line 152, in dirname
TypeError: expected str, bytes or os.PathLike object, not NoneType

Is there something wrong I am doing?
I used this command to run the debugger -

/home/rnp/Software/MOOSE/projects/moose/python/jacobiandebug/analyzejacobian.py CL_CHNS.i

[GiudGiud]

you need to provide the executable if it can't find it

/home/rnp/Software/MOOSE/projects/moose/python/jacobiandebug/analyzejacobian.py -e <path to your executable> CL_CHNS.i