Re: Hexagonal lattice points

On Jul 6, 2009, at 3:32 PM, Randy Tompkins wrote:
> I am wanting to model the band structure of a photonic crystal slab  
> (air in dielectric) with hexagonal lattice points (as opposed to  
> circles) arranged in a triangular lattice pattern.  Is this possible  
> with MPB?  If so, what code would I use for the geometry?

Yes.  I normally make a hexagon out of three blocks, e.g. with the  
following code that returns a hexagon with a given inscribed-circle  
radius, center, and material:

(define C->L (compose cartesian->lattice vector3))
(define (hexagon r c m)
   (list
    (make block (center c) (material m) (size (* r (sqrt 4/3)) (* 2 r))
	 (e1 (C->L 1 0)) (e2 (C->L 0 1)))
    (make block (center c) (material m) (size (* r (sqrt 4/3)) (* 2 r))
	 (e2 (C->L (/ (sqrt 3) 2) 0.5)) (e1 (C->L -0.5 (/ (sqrt 3) 2))))
    (make block (center c) (material m) (size (* r (sqrt 4/3)) (* 2 r))
	 (e2 (C->L (/ (sqrt 3) 2) -0.5)) (e1 (C->L 0.5 (/ (sqrt 3) 2))))
    ))

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