from ATK.KohnSham import *
import ATK

# Restore previously defined Silicon structure
si_fcc = VNLFile("si.vnl").readAtomicConfigurations()["si_fcc"]

#Specify NetCDF file for storing results
ATK.setCheckpointFilename('si_gga_dzp.nc')

# Define new KohnShamMethod using a non-default
# exchange-correlation potential (GGA)
method = KohnShamMethod(
    exchange_correlation_type = GGA.PBE,
    basis_set_parameters = basisSetParameters(type=AtomicOrbitals.DZP),
    brillouin_zone_integration_parameters = \
        brillouinZoneIntegrationParameters(monkhorst_pack_parameters = [4,4,4])
    )

# Perform the actual calculation
gga_calculation = method.apply(atomic_configuration = si_fcc)