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Non convergent solution with AC/DC - solid mechanics study on carbon nanoribbon

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Hi,

I'm new with comsol, and I'm working on my first model, but I cannot make my system converge to a solution.
I'm trying to model a suspended graphene nanoribbon (about 3.4 armstrong of thickness) with a paddle of Au in the middle, applying a potential to the ribbon and making it move due to electrostatic interaction with the substrate. I successfully completed the AC/DC simulation (the system provides in output all the data of potential, force, ecc), and applying a constant force i can also make the mechanic system converge.

My problem rise up when I try to perform the complete simulation, that never converge to a soluton. I have tried several configuration (different meshes, different solver, boundary conditions as more as possibile...) but nothing that provides a result.

Thank you in advance for any help you can provide me...


1 Reply Last Post 13 déc. 2011, 02:21 UTC−5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 13 déc. 2011, 02:21 UTC−5
Hi

some of the difficulties you have are the extreme scale differences between your Angstrom thick ribbon and the rest. Ideally such thin features should be modelled as surface elements or shells physics, but then you have a headache to link it correctly to the solids.
Because, to analyse correctly the deflection of a ribbon, you need at lest 2-3, if possible 5-8 elements in the thickness

--
Good luck
Ivar
Hi some of the difficulties you have are the extreme scale differences between your Angstrom thick ribbon and the rest. Ideally such thin features should be modelled as surface elements or shells physics, but then you have a headache to link it correctly to the solids. Because, to analyse correctly the deflection of a ribbon, you need at lest 2-3, if possible 5-8 elements in the thickness -- Good luck Ivar

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