Re: Problem with Ex and Ey

Hi Steven,

Unfortunately, it seems to be less obvious than that. I actually also tried looking at the imaginary parts and although some features can be seen (such as antinodes), they look distorted and discontinuous. 
As an example, please see Ex and Ey attached as given by MPB for an L3 cavity (3 missing holes) and that given by Akahane (APL 82 p1341). It is clear that what we see is not noise here. In fact, the image seems skewed by 60deg, despite using mpb-data to rearrange the data into a rectangular lattice. Still, not using the conversion does not give the expected fields... The frequency of the mode is correct, as well as Hz and the electric field energy density but the in-plane fields are erroneous... same result for calculations in 2D. Any further thoughts?

Regards,

Fred

On Jun 26 2007, Steven G. Johnson wrote:

>On Fri, 23 Jun 2007, F.S.F. Brossard wrote:
>> Still with the same H1 cavity, one can find another issue, this time 
>> concerning
>> the E field components. Attached are pictures of Hz, Ex, Ey. Hz gives the
>> correct field profile whereas Ex, Ey are erroneous if compared with published
>> results. The same problem can be found with other types of cavities, also for
>> different cell size, resolution, k-point, phase fixed or not, even 2D
>> calculation (hence z-even or TE)...
>
>What is happening is that, for a cavity, the E (or H) fields may be chosen 
>to be purely real (or purely imaginary). However, the output file still 
>contains both the real and imaginary parts and, if you plot the imaginary 
>part when the field is almost purely real, you are essentially plotting 
>numerical noise, and hence it looks like garbage.
>
>This is what it looks like is happening in your case.  If you are plotting 
>the real part, try plotting the imaginary part, or vice versa.
>
>Regards,
>Steven G. Johnson
>
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-- 
Frederic Brossard
Hitachi Cambridge Laboratory
Cavendish Laboratory
J J Thomson Avenue
Cambridge CB3 0HE

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