define k-path for unconventional waveguide in MPB

Dear Prof. Johnson and MPB user,
  
 For a noraml W1 waveguide, the K-path in MPB is defined like this:
=============================================
(define Gamma (vector3 0 0 0))
(define K' (lattice->reciprocal (vector3 0.5 0 0)))
(set! k-points (interpolate 50 (list Gamma K')))
==============================================
      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. 
  
       I have rather bad knowledge for reciprocal space. I read your book but I can not solve it. please help me. 
       Thank you.
  
 Sincerely 
                    
                     Ran

_______________________________________________
mpb-discuss mailing list
[email protected]
http://ab-initio.mit.edu/cgi-bin/mailman/listinfo/mpb-discuss