Dear Prof. Johnson,
I think I got your point after search the mail list.
You have already talked about this for several times.
Let me make some conclusions to help the newcomers not to make the
same mistake:
1. PML layer has no relationship with the boundary condition, but once
you set the PML in some directions,
it will make your periodic boundary in those directions do not
work (thanks to the absolutely absorption)
2. Once you set k-point to some value, your structure will have
periodic boundary conditions in all direction.
the importance is how to set the k-point.
use (set-param! k-point (vector3 Kx Ky Kz))
3. The value of the k-point determines the phase relation between the
fields (and sources) in adjacent periodic cells,
where in general the if you have period (Lx,Ly,Lz) and you are
looking at the (n,m,l) unit cell it has a phase of
exp(2*pi*i * (kx * Lx * n + ky * Ly * m+Kz*Lz*l)).
if you set the k-point to (vector3 0 0 0), that means the
fields/sources are periodic (the phase is unity from one cell to the next).
If you set the k-point to (1,0,0) it means that there is a phase
difference of exp(2*pi*L) between adjacent cells in the x direction.
In another word, the fields at one side are [image:
\exp(i\mathbf{k}\cdot\mathbf{R})] times the fields at the other side.
Thank you very much for your patient help~
Just one thing I am not sure at present:
If my computational cell is a triangular lattice like this:
+ + + + + + |y
+ + + + + |
+ + + + + + |_______X
I incident a pulse along the X direction, and I want add
periodic boundary in Y direction.
Please note in the Y direction, the fields will decay and will not
periodically repeat (though the structure are periodically repeat)
In this situation, how to set the k-point?
I would like set the k-point to (0 (sqrt 3) 0), but I am not sure.
Best wishes
Ryan
On 12/08/2008, Steven G. Johnson <[EMAIL PROTECTED]> wrote:
>
> On Aug 11, 2008, at 1:18 PM, Ryan Hao wrote:
>
> > Could you please so kind to give an example for just specify
> > one direction periodcal, and other directions PML?
>
> Please re-read what I wrote in my previous post several times and
> think about it for a few hours. Your question makes no sense. PML is
> not an alternative to periodic boundary conditions. It is not a
> boundary condition. I'm not going to keep explaining the same thing.
>
> Steven
>
> _______________________________________________
> meep-discuss mailing list
> [email protected]
> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
>
_______________________________________________
meep-discuss mailing list
[email protected]
http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/meep-discuss
