Re: woodpile band gap

Hey Matthew,

My experience is that if you use fcc lattice to write woodpile structure, 
there should be only two cylinder (or block). These two objects should be 
centered at (0 0 0) and (0.25 0.25 -0.25). Remember the space vectors are 
all based on your basis vectors.

Hope this could help.

Ziran



On Tue, 17 Feb 2009, matt wrote:

>
>
>
> I would like to simulate the textbook example of the woodpile bandgap.
>
> I based my code on the diamond crystal template in the examples
> directory, because the woodpile is also arranged on an fcc lattice.
>
> Instead of rectangular rods, I tried this with cylinders because they
> are easier to define.  The Sozuer paper indicates that these will also
> provide a bandgap.
>
> Using mayavi2, when I set the radii to be quite small, the
> visualization of the geometry appears correct.
>
> Running the simulation however shows that there is no bandgap.  Where
> there should be a bandgap, there are quite many modes.
>
> My source is below.
>
> Kind Regards,
> Matt
>
>
>
>
> ; woodpile lattice ; using diamond lattice from the example files:
> ; Dielectric spheres in a diamond (fcc) lattice.  This file is used in
> ; the "Data Analysis Tutorial" section of the MPB manual.
>
> (set! geometry-lattice (make lattice
> 			 (basis-size (sqrt 0.5) (sqrt 0.5) (sqrt 0.5))
> 			 (basis1 0 1 1)
> 			 (basis2 1 0 1)
> 			 (basis3 1 1 0)))
>
> ; Corners of the irreducible Brillouin zone for the fcc lattice,
> ; in a canonical order:
> (set! k-points (interpolate 4 (list
> 			       (vector3 0 0.5 0.5)            ; X
> 			       (vector3 0 0.625 0.375)        ; U
> 			       (vector3 0 0.5 0)              ; L
> 			       (vector3 0 0 0)                ; Gamma
> 			       (vector3 0 0.5 0.5)            ; X
> 			       (vector3 0.25 0.75 0.5)        ; W
> 			       (vector3 0.375 0.75 0.375))))  ; K
>
> ; define a couple of parameters (which we can set from the command-line)
> (define-param eps 13) ; the dielectric constant of the cylinders
> (define-param r 0.1)    ; the radius of the cylinders
>
> (define si (make dielectric (epsilon eps)))
>
>
> (set! geometry (list
> 		(make cylinder
> 		  (center 0 0 0) (radius r) (axis (vector3 1 1 0))
> 		  (height infinity) (material si))
> 		(make cylinder
> 		  (center 0 0 (/ 1 4)) (radius r) (axis (vector3 1 -1 0))
> 		  (height infinity) (material si))
> 		(make cylinder
> 		  (center 0 (/ 1 2) (/ 2 4)) (radius r) (axis (vector3 1 1 
> 0))
> 		  (height infinity) (material si))
> 		(make cylinder
> 		  (center 0 (/ 1 2) (/ 3 4)) (radius r) (axis (vector3 1 -1 
> 0))
> 		  (height infinity) (material si))
> 		))
>
>
> (set-param! resolution 24) (set-param! num-bands 10)
>
> (run)
>
>
>
> _______________________________________________
> mpb-discuss mailing list
> [email protected]
> http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
>

-------------------------------------------------
Ziran Wu
Millimeter Wave Circuits and Antennas Laboratory
Department of Electrical and Computer Engineering
University of Arizona

(520)621-6099
http://www.ece.arizona.edu/~mwca