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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Frequency Dependent Permitivity.

Posted Mar 24, 2014, 7:55 p.m. EDT Low-Frequency Electromagnetics, Materials, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Results & Visualization, Studies & Solvers Version 3.5a, Version 4.3, Version 4.3a, Version 4.3b 4 Replies

Jonathan-David Hynd
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HI Comsol Users

I am trying to model the e-filed lines expected for a PbTiO3 crystal with electrodes on top and bottom to which I apply a voltage to the top one and leave the bottom one grounded.. I can easily get a surface plot of electric potential and from that show the e-field lines for what would effectively be a DC supply.

My problem arises when I then sweep it over frequency as nothing actually changes. I know it must have something to do with my PbTiO3 substrate having a frequency dependent permittivity however I am completely clueless as to how to programme this into COMSOL.

Also once I get this I was hoping I would also be able to model the leakage current across the crystal.

Any help would be appreciated.
4 Replies Last Post Mar 25, 2014, 4:51 p.m. EDT
Robert Koslover Certified Consultant
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Posted: 1 decade ago Mar 24, 2014, 9:59 p.m. EDT
There are all sorts of reasons that you might not see any change with frequency, ranging from setting up your model improperly to setting up your post-processing improperly (or even that you simply created a model geometry where the resulting field-line distribution is nearly invariant with changing dielectric constant). I recommend you post your model file to this forum so that others may look at it and tell you what they think you did wrong, if anything.
There are all sorts of reasons that you might not see any change with frequency, ranging from setting up your model improperly to setting up your post-processing improperly (or even that you simply created a model geometry where the resulting field-line distribution is nearly invariant with changing dielectric constant). I recommend you post your model file to this forum so that others may look at it and tell you what they think you did wrong, if anything.
Jonathan-David Hynd
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Posted: 1 decade ago Mar 25, 2014, 4:39 a.m. EDT
HI Robert

Thanks for replying.

It wont let me upload the raw file as it says its too large, nor can I upload a compressed version as it doesnt accept thefile extension.

any way to get around this?
HI Robert Thanks for replying. It wont let me upload the raw file as it says its too large, nor can I upload a compressed version as it doesnt accept thefile extension. any way to get around this?
Rob Boswell COMSOL Employee

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Posted: 1 decade ago Mar 25, 2014, 7:43 a.m. EDT
Hello Jonathan,

Before uploading, you can clear the solution to greatly reduce the file size. To do this, find the study tab and then select Clear Solutions.

If necessary, you can also clear the mesh to again reduce the size of the file.

I hope this helps.

Rob
Hello Jonathan, Before uploading, you can clear the solution to greatly reduce the file size. To do this, find the study tab and then select Clear Solutions. If necessary, you can also clear the mesh to again reduce the size of the file. I hope this helps. Rob
Jonathan-David Hynd
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Posted: 1 decade ago Mar 25, 2014, 4:51 p.m. EDT
Hi Rob

Thanks for the advice, I wasnt sure if I done that, would they be able to see what I have tried to do.

Nevertheless, I cleared the solution and uploaded what I've got so far.

Just as a reminder, I am trying to model the e-field lines with an ac supply of different frequencies however I dont know how to implement a frequency dependent dielectric constant for PbTiO3


Many thanks in advanced
Hi Rob Thanks for the advice, I wasnt sure if I done that, would they be able to see what I have tried to do. Nevertheless, I cleared the solution and uploaded what I've got so far. Just as a reminder, I am trying to model the e-field lines with an ac supply of different frequencies however I dont know how to implement a frequency dependent dielectric constant for PbTiO3 Many thanks in advanced

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