import math
import meep as mp
from meep import mpb

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

sqrt_half = math.sqrt(0.5)
geometry_lattice = mp.Lattice(
    basis_size=mp.Vector3(sqrt_half, sqrt_half, sqrt_half),
    basis1=mp.Vector3(0, 1, 1),
    basis2=mp.Vector3(1, 0, 1),
    basis3=mp.Vector3(1, 1)
)

# Corners of the irreducible Brillouin zone for the fcc lattice,
# in a canonical order:
vlist = [
    mp.Vector3(0, 0.5, 0.5),        # X
    mp.Vector3(0, 0.625, 0.375),    # U
    mp.Vector3(0, 0.5, 0),          # L
    mp.Vector3(0, 0, 0),            # Gamma
    mp.Vector3(0, 0.5, 0.5),        # X
    mp.Vector3(0.25, 0.75, 0.5),    # W
    mp.Vector3(0.375, 0.75, 0.375)  # K
]

k_points = mp.interpolate(4, vlist)

# define a couple of parameters (which we can set from the command_line)
eps = 11.56  # the dielectric constant of the spheres
r = 0.25  # the radius of the spheres

diel = mp.Medium(epsilon=eps)

# A diamond lattice has two "atoms" per unit cell:
geometry = [mp.Sphere(r, center=mp.Vector3(0.125, 0.125, 0.125), material=diel),
            mp.Sphere(r, center=mp.Vector3(-0.125, -0.125, -0.125), material=diel)]

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

resolution = 16  # use a 16x16x16 grid
mesh_size = 5
num_bands = 5

ms = mpb.ModeSolver(
    geometry_lattice=geometry_lattice,
    k_points=k_points,
    geometry=geometry,
    resolution=resolution,
    num_bands=num_bands,
    mesh_size=mesh_size
)


def main():
    # run calculation, outputting electric_field energy density at the U point:
    ms.run(mpb.output_at_kpoint(mp.Vector3(0, 0.625, 0.375), mpb.output_dpwr))

if __name__ == '__main__':
    main()