Hello MPB users, To add on to Rafael's query I had problems in matching results of a paper which does calculations using plane wave expansion method itself. I had posted my query and is in archive unanswered till now :( http://www.mail-archive.com/mpb-discuss@ab-initio.mit.edu/msg00854.html
I am copying my same query here as well: I tried to reproduce the band-diagram results of a famous paper from *M*. * Notomi* : *Phys*. *Rev*. *B* 62, 10696 (*2000*) In this paper figure 7(b) shows a band-diagram of hexagonal pillars of GaAs (n = 3.6) rods of radius 0.35a in air (n = 1). It was very easy to modify the mpb example tri-rods.ctl to do the same diagram. I tried but could not match the band diagram as given in the paper ! Appearance wise both results look very similar on first hand but closer inspection shows the difference. In the paper e.g. band 5 goes from frequency value 0.56 to *0.635* (as explicitly mentioned in explanation of Fig. 6 in the same paper) but in my calculated values using mpb i get them in the range 0.56 - *0.615* (the upper frequency value doesn't match). As far as i know the results of said paper were not calculated using mpb then is this discrepancy arising because of that ? If so, then how to make sure which result is more accurate ? I'm just putting my .ctl file below for all to have a look and suggest if i made any mistake in setting up .ctl file itself or i'm missing out on something which may improve my result. Any help in this will be much appreciated. ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (set! num-bands 8) (set! geometry-lattice (make lattice (size 1 1 no-size) (basis1 (/ (sqrt 3) 2) 0.5) (basis2 (/ (sqrt 3) 2) -0.5))) (set! geometry (list (make cylinder (center 0 0 0) (radius 0.35) (height infinity) (material (make dielectric (epsilon 12.96)))))) (set! k-points (list (vector3 (/ -3) (/ 3) 0) ; K (vector3 0 0.5 0) ; M (vector3 0 0 0) ; Gamma (vector3 (/ -3) (/ 3) 0) ; K )) (set! k-points (interpolate 4 k-points)) (set! resolution 64) (run-te) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; On 11 August 2012 05:18, Rafael Gonzalez <rafael.g...@gmail.com> wrote: > Hello > > I'm trying to reproduce a paper on bandgaps for 2D lattices. These > authors report using a FEM method. I understand this approach is > different from the one that MPB uses. And so are the results. I get > very similar in shape dispersion diagrams but the bandgaps reported by > them are completely different. I thought it could be provoked for ther > lack of resolution of the simulation I ran, but the same results were > obtained. I also changed the cell size for the averaging and the block > size of the eigen solver but none of these parameters seemed to be the > reason of the discrepancy. I also thought it could be the difference > of the approaches to solve the eigenvalue problem, but I guess that a > given geometry must have a unique dispersion diagram. Numeric errors > are to be expected but I guess either one of us is doing something > wrong. Anyone has any clue? > > Best regards > > _______________________________________________ > mpb-discuss mailing list > mpb-discuss@ab-initio.mit.edu > http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss > -- ................................................................... Regards, manish http://web.iitd.ernet.in/~phz118136/
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