Dear MPB users,

I'm trying to simulate a complex 3D crystal and I want to use the supercell
instead of primitive cell. I tried to verify my code by doing the same for
diamond unit cell but the band structure that I get for diamond is
different than the one with primitive cell. I still see a bandgap but in a
higher frequency. I would like to know if anyone have any idea how we
should proceed if we were to use the supercell of a crystal?

Here is my code for the diamond supercell:

(set! geometry-lattice (make lattice
                          (basis-size 1 1 1)
                          (basis1 1 0 0)
                          (basis2 0 1 0)
                          (basis3 0 0 1)))

; 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 13) ; the dielectric constant of the spheres
 (define-param r 0.2165)    ; the radius of the spheres

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

 ; A diamond lattice has 18 "atoms" per unit cell:
 (set! geometry (list (make sphere (center      0         0         0)
(radius r)
                            (material diel))
(make sphere (center 1.0000         0         0) (radius r)
                            (material diel))
(make sphere (center 1.0000    1.0000         0) (radius r)
                            (material diel))
(make sphere (center 1.0000    1.0000    1.0000) (radius r)
                            (material diel))
(make sphere (center      0    1.0000    1.0000) (radius r)
                            (material diel))
(make sphere (center      0         0    1.0000) (radius r)
                            (material diel))
(make sphere (center 1.0000         0    1.0000) (radius r)
                            (material diel))
(make sphere (center      0    1.0000         0) (radius r)
                            (material diel))
(make sphere (center 0.5000    0.5000         0) (radius r)
                            (material diel))
(make sphere (center 0.5000    0.5000    1.0000) (radius r)
                            (material diel))
(make sphere (center      0    0.5000    0.5000) (radius r)
                            (material diel))
(make sphere (center 1.0000    0.5000    0.5000) (radius r)
                            (material diel))
(make sphere (center 0.5000         0    0.5000) (radius r)
                            (material diel))
(make sphere (center 0.5000    1.0000    0.5000) (radius r)
                            (material diel))
(make sphere (center 0.2500    0.2500    0.2500) (radius r)
                            (material diel))
(make sphere (center 0.2500    0.7500    0.7500) (radius r)
                            (material diel))
(make sphere (center 0.7500    0.7500    0.2500) (radius r)
                            (material diel))
(make sphere (center 0.7500    0.2500    0.7500) (radius r)
                            (material diel))))


 (set-param! resolution 16) ; use a 16x16x16 grid
 (set-param! mesh-size 5)
 (set-param! num-bands 10)

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

Kind regards,
*Kiumars Aryana*
M.Sc. Mechanical Engineering

Miami University
Department of Mechanical and Manufacturing Engineering, 56 Garland Hall
605 E. High St.
Oxford, OH 45056
arya...@miamioh.edu
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