How to use the gpaw.FermiDirac function in gpaw

from ase.vibrations.resonant_raman import ResonantRaman

from gpaw.cluster import Cluster
from gpaw import GPAW, FermiDirac
from gpaw.lrtddft import LrTDDFT

h = 0.25
atoms = Cluster('relaxed.traj')
atoms.minimal_box(3.5, h=h)

# relax the molecule
calc = GPAW(h=h, occupations=FermiDirac(width=0.1),
            eigensolver='cg', symmetry={'point_group': False},
            nbands=10, convergence={'eigenstates':1.e-5, 
                                    'bands':4})
atoms.calc = calc

# use only the 4 converged states for linear response calculation
rr = ResonantRaman(atoms, LrTDDFT, exkwargs={'jend':3})
rr.run()

from ase.build import molecule
from ase import optimize
from ase.vibrations.infrared import InfraRed

from gpaw.cluster import Cluster
from gpaw import GPAW, FermiDirac

h = 0.22

atoms = Cluster(molecule('H2'))
atoms.minimal_box(3.5, h=h)

# relax the molecule
calc = GPAW(h=h, occupations=FermiDirac(width=0.1))
atoms.calc = calc
dyn = optimize.FIRE(atoms)
dyn.run(fmax=0.05)
atoms.write('relaxed.traj')

# finite displacement for vibrations
ir = InfraRed(atoms)
ir.run()

from gpaw import GPAW, FermiDirac
from ase.io import read

atoms = read('opt.traj')

calc = GPAW(mode='lcao', basis='sz(dzp)', txt='gpaw.txt',
            occupations=FermiDirac(0.1),
            setups={'Ag': '11'})
atoms.calc = calc
atoms.center(vacuum=4.0)
atoms.get_potential_energy()
atoms.calc.write('groundstate.gpw')