# Problems about compositing model and MeltInterface

**URL:** <https://community.geodynamics.org/t/problems-about-compositing-model-and-meltinterface/2960>\
**Category:** ASPECT\
**Created:** [May 24, 2023, 7:50am UTC](https://community.geodynamics.org/t/problems-about-compositing-model-and-meltinterface/2960 "2023-05-24T07:50:27Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Judy](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/judy/32/1466_2.png) [@Judy](https://community.geodynamics.org/u/Judy)\
**Post date:** [May 24, 2023, 7:50am UTC](https://community.geodynamics.org/t/problems-about-compositing-model-and-meltinterface/2960/1 "2023-05-24T07:50:27Z")

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Hi all,

I’m trying to use “compositing” Material model to use the melting parameterization of the “melt simple” model with a more realistic viscosity model that provided by the “visco plastic” model.

I set like this:  
subsection Compositing  
set Viscosity = visco plastic  
set Compressibility = melt simple  
set Density = melt simple  
set Entropy derivative pressure = melt simple  
set Entropy derivative temperature = melt simple  
set Reaction terms = melt simple  
set Specific heat = melt simple  
set Thermal conductivity = melt simple  
set Thermal expansion coefficient = melt simple  
end

However, I got this error:  
**An error occurred in line \<1500\> of file \</home/ASPECT/bin/aspect/source/simulator/melt.cc\> in function**  
\*\* void aspect::MeltHandler::add\_current\_constraints(dealii::AffineConstraints&) [with int dim = 2]\*\*  
**The violated condition was: \*\*  
\*\* Plugins::plugin\_type\_matches\<const MaterialModel::MeltInterface\>(this-\>get\_material\_model())**  
**Additional information: \*\*  
\*\* Your material model does not derive from MaterialModel::MeltInterface,**  
\*\* which is required.\*\*

How can I achieve the combination of **melting parameterization** and **elastic-plastic deformation of the material**? Or can it be?

Many thanks!

Best wishes,  
Judy

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<div class="post-metadata">

**Author:** ![jdannberg](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/jdannberg/32/26_2.png) [@jdannberg](https://community.geodynamics.org/u/jdannberg)\
**Post date:** [May 25, 2023, 2:00pm UTC](https://community.geodynamics.org/t/problems-about-compositing-model-and-meltinterface/2960/2 "2023-05-25T14:00:50Z")

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Hi Judy,

As far as I know, this is currently not possible in ASPECT without changing the code. Actually, even if what you are trying right now was working, the visco plastic material model would not be able to take into account melt in its rheology, which is an important part of the rheology when you want to model magma transport (for example, you need a compaction viscosity, which the visco plastic model does not have).

Can you maybe say a bit more about what it is you want to do with the melting parameterization? Do you just need to know how much melt is there, or do you actually want to model magma transport in a visco-elasto-plastically deforming host rock? The latter is very hard to do and is an area of active research.

Best wishes,  
Juliane