# -*- coding: utf-8 -*-
# -------------------------------------------------------------
# Bulk Configuration
# -------------------------------------------------------------

# Set up lattice
lattice = SimpleCubic(3.56679*Angstrom)

# Define elements
elements = [Carbon, Carbon, Carbon, Carbon, Carbon, Carbon, Carbon, Carbon]

# Define coordinates
fractional_coordinates = [[ 0.  ,  0.  ,  0.  ],
                          [ 0.25,  0.25,  0.25],
                          [ 0.5 ,  0.5 ,  0.  ],
                          [ 0.75,  0.75,  0.25],
                          [ 0.5 ,  0.  ,  0.5 ],
                          [ 0.75,  0.25,  0.75],
                          [ 0.  ,  0.5 ,  0.5 ],
                          [ 0.25,  0.75,  0.75]]

# Set up configuration
bulk_configuration = BulkConfiguration(
    bravais_lattice=lattice,
    elements=elements,
    fractional_coordinates=fractional_coordinates
    )

# -------------------------------------------------------------
# Calculator
# -------------------------------------------------------------
k_point_sampling = MonkhorstPackGrid(
    na=8,
    nb=8,
    nc=8,
    )
numerical_accuracy_parameters = NumericalAccuracyParameters(
    k_point_sampling=k_point_sampling,
    density_mesh_cutoff=55.0*Hartree,
    )

calculator = LCAOCalculator(
    numerical_accuracy_parameters=numerical_accuracy_parameters,
    )

bulk_configuration.setCalculator(calculator)
nlprint(bulk_configuration)
bulk_configuration.update()
nlsave('bulk-diamond.hdf5', bulk_configuration)

# -------------------------------------------------------------
# Optimize Geometry
# -------------------------------------------------------------
fix_atom_indices_0 = [0, 1, 2, 3, 4, 5, 6, 7]

constraints = [FixAtomConstraints(fix_atom_indices_0)]

bulk_configuration = OptimizeGeometry(
    bulk_configuration,
    max_forces=0.05*eV/Ang,
    max_stress=0.1*GPa,
    max_steps=200,
    max_step_length=0.2*Ang,
    constraints=constraints,
    trajectory_filename=None,
    optimizer_method=LBFGS(),
    constrain_bravais_lattice=True,
)
nlsave('bulk-diamond.hdf5', bulk_configuration)
nlprint(bulk_configuration)

# -------------------------------------------------------------
# Optical Spectrum
# -------------------------------------------------------------
kpoint_grid = MonkhorstPackGrid(
    na=22,
    nb=22,
    nc=22,
    )

optical_spectrum = OpticalSpectrum(
    configuration=bulk_configuration,
    kpoints=kpoint_grid,
    energies=numpy.linspace(0,1,21)*eV,
    broadening=0.1*eV,
    bands_below_fermi_level=100,
    bands_above_fermi_level=100,
    )
nlsave('bulk-diamond.hdf5', optical_spectrum)