Help: inverse shell opal

Dear MPB user and St.V.Johnson,

 I wish to calculate the band diagram of a overlapping titania shell 
hollow model ( inverse opal). I wonder my calculation is correct since 
the result is different from the transmission spectra:


 

(set! default-material (make dielectric (epsilon 1)))

 (set! geometry-lattice (make lattice

                          (basis-size (sqrt 0.5) (sqrt 0.5) (sqrt 0.5))

                          (basis1 0 1 1)

                          (basis2 1 0 1)

                          (basis3 1 1 0)))

 

 (set! k-points (interpolate 4 (list

                                (vector3 0 0.5 0.5)            ; X

                                (vector3 0 0.625 0.375)        ; U

                                (vector3 0 0.5 0)              ; L

                                (vector3 0 0 0)                ; Gamma

                                (vector3 0 0.5 0.5)            ; X

                                (vector3 0.25 0.75 0.5)        ; W

                                (vector3 0.375 0.75 0.375))))  ; K

 

;(define-param rbig 0.380953778)    ; sphere of shell

;(define-param rsmall 0.35355339)    ; radius of the air spheres

(define diel1 (make dielectric (epsilon 1)))

(define diel2 (make dielectric (epsilon 6.25)))

(set! geometry (list (make sphere (center 0) (radius 0.380953778) ; make 
titania shell

                           (material diel2))

                     (make sphere (center 0) (radius 0.35355339)

; make air sphere

                           (material diel1))

                     ))

 (set-param! resolution 16)

 (set-param! mesh-size 10)

 (set-param! num-bands 20)

(run)


thanks in advance