Dear Steven and MPB users,
I have just started using MPB and am trying to understand its potential.
To get started I just ran the square lattice .ctl file:
; A simple square lattice of cylinders in 2D.
(set! num-bands 8)
(set! geometry-lattice (make lattice (size 1 1 no-size)
(basis1 1 0)
(basis2 0 1)
))
(set! default-material (make dielectric (epsilon 3.61)))
(set! geometry (list (make cylinder
(center 0 0 0) (radius 0.2) (height infinity)
(material (make dielectric (epsilon 1.96)))
)))
(set! k-points (list (vector3 0 0 0) ; Gamma
(vector3 0.5 0 0) ; X
(vector3 0.5 0.5 0) ; M
(vector3 0 0 0))) ; Gamma
(set! k-points (interpolate 6 k-points))
(set! resolution 32)
(run-tm)
(run-te)
(output-epsilon)
Next I changed the lattice size of the above .ctl file and made it twice.
But at the same time I didn't want the structure to change so I added three
extra cylinders for each lattice point (The structure was indeed same in my
knowledge as I could see from the generated epsilon output file).
; A simple modified square lattice of cylinders in 2D.
(set! num-bands 8)
(set! geometry-lattice (make lattice (size 2 2 no-size)
(basis1 1 0)
(basis2 0 1)
))
(set! default-material (make dielectric (epsilon 3.61)))
(set! geometry (list (make cylinder
(center 0 0 0) (radius 0.2) (height infinity)
(material (make dielectric (epsilon 1.96))))
(make cylinder
(center 1 0 0) (radius 0.2) (height infinity)
(material (make dielectric (epsilon 1.96))))
(make cylinder
(center 0 1 0) (radius 0.2) (height infinity)
(material (make dielectric (epsilon 1.96))))
(make cylinder
(center 1 1 0) (radius 0.2) (height infinity)
(material (make dielectric (epsilon 1.96))))
))
(set! k-points (list (vector3 0 0 0) ; Gamma
(vector3 0.5 0 0) ; X
(vector3 0.5 0.5 0) ; M
(vector3 0 0 0))) ; Gamma
(set! k-points (interpolate 4 k-points))
(set! resolution 32)
(set! mesh-size 6)
(run-tm)
(run-te)
(output-epsilon)
Now running this new .ctl file gave band-structure which were strange in
someway. I am not sure if I have just encountered what is refereed to as
band-folding.
Whatever the case may be can someone guide me to see how the two band
structures are related with each other (They must be related as I have not
changed the structure OR have I ?)
It may be possible that this point has already been discussed in the mailing
list. In that case I am sorry for posting my query but please provide me
with the link of the discussion so that I may get some hint from there.
Thank you for your kind consideration.
--
...................................................................
With best regards,
Manish Kumar
MSc(Physics) Sri Sathya Sai University
M.Tech Applied Optics (Dept.of Physics)
IITDelhi
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