# Issues: Multicomponent model

**URL:** <https://community.geodynamics.org/t/issues-multicomponent-model/572>\
**Category:** ASPECT\
**Created:** [April 13, 2019, 8:08am UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572 "2019-04-13T08:08:18Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![sungho](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/sungho/32/365_2.png) [@sungho](https://community.geodynamics.org/u/sungho)\
**Post date:** [April 13, 2019, 8:08am UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/1 "2019-04-13T08:08:18Z")

</div>

Hello.  
I’m a newcomer of “ASEPCT”.  
The cookbook seems good enough to start “ASPECT” but it’s quite difficult for me.  
Like the jelly fish problem in Cookbook, I drew a simple subduction model in 2D using Inkscape and converted the figure into ascii values (x, y, phase).

Then, loading the file, however, an error occurs in some conditions.  
Following in condition A, no error occur and the result show like as I expect.  
It says two thing : the external material index file has no problem and input is not wrong, I believe.

But, following condition B and C, they are not working well.

I can’t understand. Any one has solutions?

# subduction\_test.txt includes x, y, phase(0, 1, 2). Phase denotes for mantle, two continental plates.

# Condition A:

subsection Compositional fields  
set Number of fields = 1  
end

subsection Initial composition model  
set Model name = ascii data  
subsection Ascii data model  
set Data directory = /home/sungho/Geodynamics/subduction\_test/  
set Data file name = subduction.txt  
end  
end

subsection Material model  
set Model name = multicomponent  
subsection Multicomponent  
set Densities = 3200  
set Specific heats = 1000  
set Thermal conductivities = 2.5  
set Thermal expansivities = 3.e-5  
set Viscosities = 1.0e21  
end  
end

# Condtion B:

subsection Compositional fields  
set Number of fields = 3  
end

subsection Initial composition model  
set Model name = ascii data  
subsection Ascii data model  
set Data directory = /home/sungho/Geodynamics/subduction\_test/  
set Data file name = subduction.txt  
end  
end

subsection Material model  
set Model name = multicomponent  
subsection Multicomponent  
set Densities = 3200  
set Specific heats = 1000  
set Thermal conductivities = 2.5  
set Thermal expansivities = 3.e-5  
set Viscosities = 1.0e21  
end  
end

# Condition C:

subsection Compositional fields  
set Number of fields = 1  
end

subsection Initial composition model  
set Model name = ascii data  
subsection Ascii data model  
set Data directory = /home/sungho/Geodynamics/subduction\_test/  
set Data file name = subduction.txt  
end  
end

subsection Material model  
set Model name = multicomponent  
subsection Multicomponent  
set Densities = 3200, 3200, 3200  
set Specific heats = 1000, 1000, 1000  
set Thermal conductivities = 2.5, 2.5, 2.5  
set Thermal expansivities = 3.e-5, 3.e-5, 3.e-5  
set Viscosities = 1.0e21, 1.0e21, 1.0e21  
end  
end

---

<div class="post-metadata">

**Author:** ![bangerth](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/bangerth/32/52_2.png) [@bangerth](https://community.geodynamics.org/u/bangerth)\
**Post date:** [April 13, 2019, 8:58pm UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/2 "2019-04-13T20:58:11Z")

</div>

Sungho: Can you state what error you get precisely?  
Best  
W.

---

<div class="post-metadata">

**Author:** ![sungho](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/sungho/32/365_2.png) [@sungho](https://community.geodynamics.org/u/sungho)\
**Post date:** [April 15, 2019, 1:12am UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/3 "2019-04-15T01:12:41Z")

</div>

In advance, I appreciate your attention to mine.

It shows quite long lines. I don’t know which are specifically related to main the error.  
Please understand what I have faced difficulties.  
Plus, if you want to have a look at my input files, I can email you.

Thanks

Best regards

Sungho

# this is that ASPECT shows me

 ![Screenshot%20from%202019-04-15%2010-15-19](https://canada1.discourse-cdn.com/flex036/uploads/geodynamics/original/1X/2e1d52015f1a77f40bb3e393b67bc9c334a86215.png)

---

<div class="post-metadata">

**Author:** ![tjhei](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/tjhei/32/1163_2.png) [@tjhei](https://community.geodynamics.org/u/tjhei)\
**Post date:** [April 15, 2019, 2:51am UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/4 "2019-04-15T02:51:49Z")

</div>

Are you specifying the field “Densities” in the material model? If yes, how? This is what the error message is saying.

---

<div class="post-metadata">

**Author:** ![sungho](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/sungho/32/365_2.png) [@sungho](https://community.geodynamics.org/u/sungho)\
**Post date:** [April 15, 2019, 3:43am UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/5 "2019-04-15T03:43:12Z")

</div>

I assign field names from the external file(subduction.txt).  
Then, I specify field densities using multicomponent model like below way.

subsection Compositional fields  
set Number of fields = 1  
end

subsection Initial composition model  
set Model name = ascii data  
subsection Ascii data model  
set Data directory = /home/sungho/Geodynamics/subduction\_test/  
set Data file name = subduction.txt  
end  
end

subsection Material model  
set Model name = multicomponent  
subsection Multicomponent  
set Densities = 3200, 3200, 3200  
set Specific heats = 1000, 1000, 1000  
set Thermal conductivities = 2.5, 2.5, 2.5  
set Thermal expansivities = 3.e-5, 3.e-5, 3.e-5  
set Viscosities = 1.0e21, 1.0e21, 1.0e21  
end  
end

---

<div class="post-metadata">

**Author:** ![tjhei](https://yyz2.discourse-cdn.com/flex036/user_avatar/community.geodynamics.org/tjhei/32/1163_2.png) [@tjhei](https://community.geodynamics.org/u/tjhei)\
**Post date:** [April 16, 2019, 2:58pm UTC](https://community.geodynamics.org/t/issues-multicomponent-model/572/6 "2019-04-16T14:58:14Z")

</div>

The documentation of the parameter says

```auto
"List of densities for background mantle and compositional fields,"
"for a total of N+1 values, where N is the number of compositional fields."
"If only one value is given, then all use the same value. Units: $kg / m^3$");

```

As you have one compositional field, you need to provide 1 or 2 values (but not 3).