Hexagonal Si rod

Dear Steven, dear all,

Currently, I am doing study on photonic crystals in my university. I used
mpb-1.4.2 to simulate the photonic bandgap. I faced some problems and 
hope to
get helps from professor.I tried to simulate a photonic crystal's structure
which is hexagonal rods in air. To obtain square lattice hexagonal rods in
air, I did this.
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; *** 3D periodic dielectric layered structure with omnidirectional
; photonic band gap ***
(print "********** Square lattice of Si rods in air **********\n")
(set! num-bands 8)
(set! geometry-lattice (make lattice (size 1 1 no-size)))
(set! geometry (list   (make block
                        (center 0.06 1.1 0)
                        (material (make dielectric (epsilon 12)))
		       (size 0.259 0.259 infinity)
		       (e1 1 0 0)
		       (e2 -0.5 0.866 0)
		       (e3 0 0 1))
		       (make block
                        (center 0.06 -1.1 0)
                        (material (make dielectric (epsilon 12)))
		       (size 0.259 0.259 infinity)
		       (e1 1 0 0)
		       (e2 -0.5 -0.866 0)
		       (e3 0 0 1))
		       (make block
                        (center -0.12 0 0)