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September 2, 2010 2:48pm UTC

Boundary condition on metal-air interface

Dear Forum-User,

in my current simulations (Comsol version 4.0a) I try to model the interaction of light (plane-wave; IR) with a metallic nano-structures.
I set the structure to be made of gold defined by its dielectric losses using Drude model (implemented as an analytic function depending on the frequency). The metallic strucutre is surrounded by air. The simulation volume is embedded in PMLs. The model is solved time-harmonic/stationary (Helmholtz).
My problem is now, that Comsol defines the boundary between air and metal automatically. Sometimes it is set automatically to PEC, which is surely not what I need. In other cases these boundaries are just not applicable. In older Comsol versions such boundaries could be set to continuity. It seems to me that this is not possible anymore in Comsol 4 by means of manual setting.
I can for sure set the boundary to be e.g. a 'impedance boundary' but I want to resolve the skin depth.

Maybe one of you has an idea, what I am doing wrong.

Thank you very much in advance.

Greetings,
Peter

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