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Eigenvalue solver in COMSOL
Posted 24 mai 2016, 11:20 UTC−4 Version 5.1, Version 5.2 4 Replies
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I am solving a PDE in COMSOL with the eigenvalue solver. When I compute the solution I get only one solution when in reality I should get an infinite number of eigenmodes. How do I access the different eigenmodes and more importantly: In what order does COMSOL give me the eigenmodes? Does it start from the lowest eigenvalue and work its way up depending on the number of eigenvalues you demanded?
4 Replies Last Post 26 mai 2016, 08:26 UTC−4
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Posted:
8 years ago
Hi
Which physics are you using ?,
Normally you can define how many of the eigenfrequencies/eigenvalues respectively you want to display, and depending on the physics COMSOl might set the default to "1". But clearly COMSOL, as numerical tool, cannot propose an "infinite" number of eigenmodes, it must be finite for the software to be able to list them ;) The more you want the more you need to mesh fine and the more time it takes ...
--
Good luck
Ivar
Which physics are you using ?,
Normally you can define how many of the eigenfrequencies/eigenvalues respectively you want to display, and depending on the physics COMSOl might set the default to "1". But clearly COMSOL, as numerical tool, cannot propose an "infinite" number of eigenmodes, it must be finite for the software to be able to list them ;) The more you want the more you need to mesh fine and the more time it takes ...
--
Good luck
Ivar
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Posted:
8 years ago
My script is this. I want to solve the Schrodinger equation for the geometry defined in the script and this is the only way I can see how to do it.
In the link:
www.lmn.pub.ro/~daniel/ElectromagneticModelingDoctoral/Books/COMSOL4.3/mph/PhysicsInterfaceBuilderUsersGuide.pdf
There is a long step-by-step guide to set up a physics interface for the Schrodinger equation but I could not follow it because it was written to users of COMSOL which apparently is very different from the 5.1 version I am using.
Either way the solver is not working in my script. The eigenvalues found do not make sense if they are to be the ground state, first excited state energies etc. Also how do I browse between the different eigensolutions? I would expect there to be one solution/eigenmode for each eigenvalue.
In the link:
www.lmn.pub.ro/~daniel/ElectromagneticModelingDoctoral/Books/COMSOL4.3/mph/PhysicsInterfaceBuilderUsersGuide.pdf
There is a long step-by-step guide to set up a physics interface for the Schrodinger equation but I could not follow it because it was written to users of COMSOL which apparently is very different from the 5.1 version I am using.
Either way the solver is not working in my script. The eigenvalues found do not make sense if they are to be the ground state, first excited state energies etc. Also how do I browse between the different eigensolutions? I would expect there to be one solution/eigenmode for each eigenvalue.
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Posted:
8 years ago
Hi
have you checked the model "Physics Builder" documentation, there you have the development of the Schrodinger equations for COMSOL
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Good luck
Ivar
have you checked the model "Physics Builder" documentation, there you have the development of the Schrodinger equations for COMSOL
--
Good luck
Ivar
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Posted:
8 years ago
Thank you for the suggestion.
I have now set up a physics builder that solves the Schrodinger equation given some geometry and input potential. What I would like to do however, is to be able to solve it where I specify different values for the potential V depending on the domain. If I try to do that for for example two circles with common origin I get a solution that does not make sense. Can you show me in the attached script how you would make V a stepwise function that takes two different values a and b in the outer and inner ring?
I have now set up a physics builder that solves the Schrodinger equation given some geometry and input potential. What I would like to do however, is to be able to solve it where I specify different values for the potential V depending on the domain. If I try to do that for for example two circles with common origin I get a solution that does not make sense. Can you show me in the attached script how you would make V a stepwise function that takes two different values a and b in the outer and inner ring?
Attachments: