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Entities needing a material

Posted 15 gen 2021, 01:12 GMT-5 MEMS & Nanotechnology, Semiconductor Devices, MEMS & Piezoelectric Devices Version 5.4 3 Replies

Poorvank Sharma Teaching Assistant | IIT Bombay | Vibrational Spectroscopy
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The below post is related to an archived discussion

I have a silicon wafer with a nickel nanostructure on top of it. I have assigned the material accordingly and still for the top and bottom surface, there is an error of Entities needing a material. I have tried closing and reopening. Didn't work!. Can anyone help me with this issue?

I m attaching the .mph file.

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3 Replies Last Post 20 gen 2021, 01:55 GMT-5
Henrik Sönnerlind COMSOL Employee

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Posted: 4 years ago 15 gen 2021, 07:01 GMT-5

This is a common mistake. If you have both domain and boundary features that uses From Material, then the materials must be assigned not only to domains, but also to boundaries. Boundaries do not inherit domain materials.

This means that you have to add the same material twice, but with different types of selection. Even better, add the material once under Global Definitions, and use two Material Link nodes to connect it to both domains and boundaries.

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Henrik Sönnerlind
COMSOL
This is a common mistake. If you have both domain and boundary features that uses **From Material**, then the materials must be assigned not only to domains, but also to boundaries. Boundaries do not inherit domain materials. This means that you have to add the same material twice, but with different types of selection. Even better, add the material once under **Global Definitions**, and use two **Material Link** nodes to connect it to both domains and boundaries.
Poorvank Sharma Teaching Assistant | IIT Bombay | Vibrational Spectroscopy
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Posted: 4 years ago 18 gen 2021, 01:07 GMT-5
Updated: 4 years ago 19 gen 2021, 00:39 GMT-5

Hi Henrik

Do you have any tutorial by any chance for the Global Definitions approach? It would be helpful. Also, I have 2 different materials sharing a common boundary. I am not sure how to assign the boundary as a particular material.

Regards

Poorvank

Hi Henrik Do you have any tutorial by any chance for the Global Definitions approach? It would be helpful. Also, I have 2 different materials sharing a common boundary. I am not sure how to assign the boundary as a particular material. Regards Poorvank
Henrik Sönnerlind COMSOL Employee

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Posted: 4 years ago 20 gen 2021, 01:55 GMT-5

For the Global Defintions approach:

  1. When you add the material you select Add to Global Material instead of Add to Component.
  2. Under Materials in the component, you add More Materials -> Material Link
  3. In the Material Link node, you select the global material you want and the geometrical selection.

It is (for physical reasons) uncommon that there are two materials sharing a common boundary. But if this really is the case, you cannot use From Material for both of them. In one of the physics nodes using material data you have to enter the data manually as User Defined.

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Henrik Sönnerlind
COMSOL
For the Global Defintions approach: 1. When you add the material you select **Add to Global Material** instead of **Add to Component**. 2. Under **Materials** in the component, you add **More Materials -> Material Link** 3. In the **Material Link** node, you select the global material you want and the geometrical selection. It is (for physical reasons) uncommon that there are two materials sharing a common boundary. But if this really is the case, you cannot use **From Material** for both of them. In one of the physics nodes using material data you have to enter the data manually as **User Defined**.

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