4fold symmetry of bands in 6fold symmetry structure...

Hi all,

my problem is the following:

although i defined a hexagonal structure in epsilon, the bands have 
rather 4fold symmetry (see attachments). I just don't get the clou!

Any help is appreciated!

Joachim Kalden

-----------------------code-------------------------------
(define-param dnws 1) ;diameter of nanowire
(define-param zno 6.15) ;index of nanowire

(set! num-bands 100)

(set! geometry-lattice (make lattice (size 4 4 no-size)))

(set! geometry (list
            (make block
			(center 0 (/ dnws 4) 0)		
		       (e1 (/ (sqrt 3) 2) -0.5 0)
			(e2 (/ (sqrt 3) -2) -0.5 0)
                       	(size (/ dnws 2) (/ dnws 2) 0)
			(material (make dielectric (epsilon zno))))
            (make block
			(center 0 (/ dnws -4) 0)		
		       (e1 (/ (sqrt 3) 2) -0.5 0)
			(e2 (/ (sqrt 3) -2) -0.5 0)
                      	(size (/ dnws 2) (/ dnws 2) 0)
			(material (make dielectric (epsilon zno))))
            (make block
			(center 0 0 0)		
			(size (/ (* dnws (sqrt 3)) 2) (/ dnws 2) 0)
			(material (make dielectric (epsilon zno))))
))

(set! k-points (list (vector3 0 0 0)          ; Gamma
                       (vector3 0 0.5 0)        ; M
                       (vector3 (/ -3) (/ 3) 0) ; K
                       (vector3 0 0 0)))        ; Gamma
(set! k-points (interpolate 4 k-points))

(set! mesh-size 5)
(set! resolution 32)

(run-tm (output-at-kpoint (vector3 0 0 0)
                            fix-efield-phase output-efield-z))
(run-te)