Re: define k-path for unconventional waveguide in MPB

On Sep 2, 2009, at 11:44 PM, ryanhao wrote:
> ==============================================
>       but how about the repeated unit takes 2 lattice constant? how  
> to define the K-path? see attached.
>        I have tried to decrease the reciprocal lattice to 1/2 of its  
> previous value, but the result is wrong.

It's hard to answer your question without knowing what your lattice  
vectors are.

If your lattice vectors (in geometry-lattice) are orthogonal, with the  
first lattice vector oriented along the direction of the waveguide, then

	(set! k-points (interpolate 50 (list (vector3 0) (vector3 0.5))))

is correct: the edge of the Brillouin zone is 1/2 of the first  
reciprocal lattice vector.  (Note that by doubling your period in the  
propagation direction, you halve the first reciprocal lattice vector,  
halving the size of the Brillouin zone, so the band diagram is  
"folded" in two compared to the usual W1 waveguide.)

It's only if you have non-orthogonal lattice vectors that things  
become trickier.

Steven