woodpile band gap

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)