I shift the rows of PCW in y deirection but epsilon show the rows are shifted in x too. Why?

Dear MPB users

I am studying the effect of the defect width  of PC waveguide on dispersion curve.
The CTL file is attached.
first I erase three  row of the holes in middle, and add two rows with a displacement in y direction.
As you see the attached epsilon files for different displacement, you can see the rows are shifted in x direction as well.

1- why? can any body help? I did not shift rows in x direction! (as you see in ctl file);

2-
as it is clear, the epsilon pictures are not triangular crystal any
more! shall I shift rows in -x direction to compensate the above
mentioned unwanted shift and let to study the effect of width only (not
affected by shift in x direction)?

Regards
Hassan


Part of CTL file
================
(define-param displacement-in+y-direction 1.25)
(define-param displacement-in-y-direction -1.25)
(set! geometry (list (make cylinder                 (center 0 0 0) (radius r) (height infinity)      (material air))))
(set! geometry 
    (append
            (geometric-objects-lattice-duplicates geometry)
                 (list 
                ;add a rod of epsilon on Center, to erase a row of rods and form a waveguide:
                (make cylinder (center 0 0 0) (radius r) (height infinity)
                        (material (make dielectric (epsilon eps)))
                )
                ; add a rod of eps belowe, to fill a row of air
                (make cylinder (center 0 1 0) (radius r) (height infinity)
                              (material (make dielectric (epsilon eps)))
                )
                ; add a rod of eps above, to fill a row
                (make cylinder (center 0 -1 0) (radius r) (height infinity)
                              (material (make dielectric (epsilon eps)))
                )
                ; add a closer row above
                (make cylinder (center 0 displacement-in-y-direction 0) (radius r1) (height infinity)
                              (material air);(make dielectric (epsilon eps)))
                )
                 ; add a closer row belowe
                (make cylinder (center 0 displacement-in+y-direction 0) (radius r1) (height infinity)
                              (material air);(make dielectric (epsilon eps)))
                )


            )
        )
)
==================

_______________________________________________
mpb-discuss mailing list
[email protected]
http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss