; A line-defect waveguide in a 2d triangular lattice of dielectric ; rods (c.f. tri-rods.ctl), formed by a row of missing rods along the ; "x" direction. (Here, "x" and "y" refer to the first and second ; basis directions.) This structure supports a single guided band ; within the band gap, much like the analogous waveguide in a square ; lattice of rods (see "Photonic Crystals" by Joannopoulos et al.).
(define-param supercell-y 7) ; the (odd) number of lateral supercell periods
(set! geometry-lattice (make lattice
(basis1 (/ (sqrt 3) 2) 0.5)
(basis2 (/ (sqrt 3) 2) -0.5)
(size 1 supercell-y no-size)))
(define-param eps 12) ; the dielectric constant of the rods
(define-param r 0.2) ; the rod radius in the bulk crystal
(set! geometry (list (make cylinder
(center 0 0 0) (radius r) (height infinity)
(material (make dielectric (epsilon eps))))))
(set! geometry
(append
; duplicate the bulk crystal rods over the supercell:
(geometric-objects-lattice-duplicates geometry)
; add a rod of air, to erase a row of rods and form a waveguide:
(list
(make cylinder (center 0) (radius r) (height infinity)
(material air)))))
(define Gamma (vector3 0 0 0))
(define K' (lattice->reciprocal (vector3 0.5 0 0))) ; edge of Brillouin
zone.
(set! k-points (interpolate 4 (list Gamma K'))) ; the bigger the supercell, the more bands you need to compute to get ; to the defect modes (the lowest band is "folded" supercell-y times):(define-param extra-bands 5) ; number of extra bands to compute above the gap
(set! num-bands (+ supercell-y extra-bands))
(set-param! resolution 32)
; Compute the TM modes, outputting the Ez field in the *middle* of the
; band. (In general, the guided mode in such an air defect may have
; exited the gap by the time it reaches the edge of the Brillouin
; zone at K'.)
(run-tm
(output-at-kpoint (list-ref k-points (quotient (length k-points) 2))
fix-efield-phase output-efield-z))
----- Original Message -----
From: "Steven G. Johnson" <[EMAIL PROTECTED]>
To: <mpb-discuss@ab-initio.mit.edu> Sent: Sunday, April 30, 2006 12:00 PM Subject: Re: [MPB-discuss] repeated bands while using MPI-MPB
On Sun, 30 Apr 2006, Lingling Tang wrote:I am using MPI-MPB (Linux 2.4.21-37.0.1.EL, gcc 3.2.3, mpich) to analyze 2D photonic crystal, such as supercell and line defect structure. It is strange that for the same control file, I get different band digram when I use one and two processors. The result got by one processor is correct, while repeated bands are obtained if two processors are used. For example, if num-bands is 16, 9th band to 16th is exactly the same as 1st to 8th. I can never go to higher frequency by increasing num-bands. Does anyone have any idea about this problem?That doesn't make any sense to me. Perhaps you are running it incorrectly? You should use something likempirun -np 2 mpb-mpi foo.ctlAnother problem with MPI-MPB is the first two dimensions transposed as mentioned in user reference. Use mpb-data -r -n 32 epsilon.h5, I still cannot get correct image (I can if use non-mpi version mpb). Is there any thing wrong with my commands?Just pass the -T option to mpb-data, as described in the manual. _______________________________________________ mpb-discuss mailing list mpb-discuss@ab-initio.mit.eduhttp://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss
band diagram.pdf
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