; Dielectric spheres in a diamond (fcc) lattice.  This file is used in
; the "Data Analysis Tutorial" section of the MPB manual.

(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)))

; Corners of the irreducible Brillouin zone for the fcc lattice,
; in a canonical order:
(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 a couple of parameters (which we can set from the command-line)
(define-param eps 11.56) ; the dielectric constant of the spheres
(define-param r 0.25)    ; the radius of the spheres

(define diel (make dielectric (epsilon eps)))

; A diamond lattice has two "atoms" per unit cell:
(set! geometry (list (make sphere (center 0.125 0.125 0.125) (radius r) 
			   (material diel))
		     (make sphere (center -0.125 -0.125 -0.125) (radius r) 
			   (material diel))))

; (A simple fcc lattice would have only one sphere/object at the origin.)

(set-param! resolution 16) ; use a 16x16x16 grid
(set-param! mesh-size 5)
(set-param! num-bands 5)

; run calculation, outputting electric-field energy density at the U point:
(run (output-at-kpoint (vector3 0 0.625 0.375) output-dpwr))