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January 18, 2010 8:43pm UTC in response to Martina Abb

Re: Problem with Mie Model

Play with meshing more.
Define it manually with care, sometimes automatic meshing give you better results (avoiding inverted elements) but could be not enough for nanoscale.

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March 15, 2010 8:54am UTC in response to jiekorea gaojie

Re: Problem with Mie Model

Hi

I believe there is a quick reply for your units issue the "r/1[m]" this gives [m] if "r" is without units, or [m^2] as I expect "r" is in [m] and is different from "r/(1[m])" which is without units or equivalent to understanding it as (r[m])/(1[m])

Will have to look closer for the global expression, but I'm a t a Comsol course just now ;) and Ihave to liten to the speaker too ;)

Have a nice day
Ivar

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April 16, 2010 11:13am UTC in response to Michael Petrov

Re: Problem with Mie Model

Hi everyone!

I have the same problem with the model; for some wavelengths the scattering cross section becomes negative which makes, of course, nonsense. First I thought it was probably a mistake I made while defining the global expressions or the integration ones, so I repeated the process several times but I obtained the same result over and over. Later I thought that maybe one of the steps in the documentation file was wrong, so I ended downloading the file .mph directly from the model gallery instead of trying to reproduce it myself. Everything was already defined in the file so I just had to mesh the model and solve it. To do so I followed the instructions (mesh size, number of layers in the exterior subdomain, solver parameters,...) exactly as they were written in the documentation. It was a big surprise to find out that I had exactly the same problem as before. I wanted to attach the scattering cross-sections obtained with the downloaded file (Mie_scattering_plasmonic_reset_35a1.mph) to illustrate the problem but the attach button is not responding. Anyway, any idea about what could be wrong?

Thanks a lot,

Ramon

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November 2, 2010 10:22am UTC in response to Shakeeb Bin Hasan

Re: Problem with Mie Model

Are you using COMSOL version 3.5?
I had the same problem, but it was solved after installing the latest hotfix.

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November 22, 2011 4:07pm UTC in response to keya zhou

Re: Problem with Mie Model

Hi,

I am trying to use the variables defined in the Mie scattering tutorial and have found out that sc should be replaced with mod1.rfw.rel, for the E components and just rfw. for the H components. For example 0.5*real(mod1.rfw.relEx*0.25*conj(relHz)-mod1.rfw.relEy*0.25*conj(relHx)). The power variables are called Poavx instead of Poxav and the sc should again be replaced with rel. Poxav_rfw is mod1.rfw.Poavx in v4.2a.

But even though I have changed this in my model I can't get it to work because I still get the error "unexpected unit of input" for the dsigma_far variable : (normEfar^2/(r/(1[m]))^2)/abs(E0)^2*r^2 where r is defined as sqrt(x^2+y^2+z^2)

In equation view under far field calculation tab I see that the normEfar is in V/m units and so is E0 so the expression should give me units of m^2 which is what I want.

Does anybody know how to fix this error?

thanks in advance,
Signe

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November 22, 2011 5:57pm UTC in response to Ivar Kjelberg

Re: Problem with Mie Model

Hi,

I tried to run my program but I don't get any data for the different cross sections. I'm not trying to replicate the Mie scattering tutorial but rather trying to use some of the variables in my own model with a gold nano cavity so I can get the spectra. I think there is a problem with my integration and the parametric sweep over wavelengths, is it possible you can take a quick look at it?
Do you know what the best way is to obtain a reflectivity spectrum?

regards Signe

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