hi all,
I want to simulate a 3D slab of rods (see attached file rods-3d.ctl). I
started with the 2D case and supposed that, if the slab fills the cell
entirely in the z direction, I'd find the same band diagram as in 2D.
However, I don't, and I don't either understand why. With increasing z,
one can see flat bands appearing here and there.
I don't see for what kind of physical reason that may happen. Therefore,
I thought of groping around the following things:
1) influence of the resolution for fixed z
2) influence of the mesh size for fixed z
3) influence of the cell size (in z)
4) influence of the number of bands
Nothing seems to help. Changing z is the only thing that really makes a
difference and it's the only thing that shouldn't.
Now I'm running out of ideas. Does anybody have a clue?
(define-param r 0.3) ; radius of cylinders
(define-param nout 1.457) ; index of outer medium
(define-param n 1.5) ; index of slab
(define-param rodn 3.52) ; index of cylinders
(define-param z 2.0) ; cell height
(define-param sthk 0.4) ; slab thickness
(define-param resol 48) ; resolution
(define-param mesh 10) ; mesh size
(define-param nb 8) ; number of bands
(set! geometry-lattice (make lattice (size 1 1 z)
(basis1 (/ (sqrt 3) 2) 0.5 0)
(basis2 (/ (sqrt 3) 2) -0.5 0)
(basis3 0 0 1)
))
(set! resolution resol)
(set! num-bands nb)
(set! mesh-size mesh)
(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 96 k-points))
(set! default-material (make dielectric (index nout)))
(set! geometry (list
(make block
(center 0 0 0) (size 1 1 sthk)
(material (make dielectric (index n))))
(make cylinder
(center 0 0 0) (radius r) (height sthk)
(material (make dielectric (index rodn))))
))
(run-zeven)
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