How to use the gpaw.PoissonSolver function in gpaw

from __future__ import print_function, division
import os,unittest,numpy as np

try:
  from ase import Atoms
  from gpaw import GPAW
  fname = os.path.dirname(os.path.abspath(__file__))+'/h2o.gpw'

  from gpaw import PoissonSolver
  atoms = Atoms('H2O', positions=[[0.0,-0.757,0.587], [0.0,+0.757,0.587], [0.0,0.0,0.0]])
  atoms.center(vacuum=3.5)
  convergence = {'density': 1e-7}     # Increase accuracy of density for ground state
  poissonsolver = PoissonSolver(eps=1e-14, remove_moment=1 + 3)     # Increase accuracy of Poisson Solver and apply multipole corrections up to l=1

  # hgh and sg15 setups works only with minimal basis set!
  calc = GPAW(xc='LDA', h=0.3, nbands=6,
        convergence=convergence, poissonsolver=poissonsolver,
        mode='lcao', txt=None, setups="hgh")     # nbands must be equal to norbs (in this case 6)
  atoms.set_calculator(calc)
  atoms.get_potential_energy()    # Do SCF the ground state
  calc.write(fname, mode='all') # write DFT output

except:
  calc = None



class KnowValues(unittest.TestCase):

'DM.Tolerance': 1e-4,
               'DM.MixingWeight': 0.01,
               'MaxSCFIterations': 150,
               'DM.NumberPulay': 4})

    H2O.set_calculator(siesta_calc)
    efree_siesta = H2O.get_potential_energy()

    # run gpaw
    from gpaw import GPAW, PoissonSolver
    H2O_gp = Atoms("H2O", np.array([[0.0, -0.757, 0.587],
                                 [0.0, +0.757, 0.587],
                                 [0.0, 0.0, 0.0]]))
    H2O_gp.center(vacuum=3.5)
    convergence = {'density': 1e-7}
    poissonsolver = PoissonSolver(eps=1e-14, remove_moment=1 + 3)
    gpaw_calc = GPAW(xc='PBE', h=0.3, nbands=6,
            convergence=convergence, poissonsolver=poissonsolver,
            mode='lcao', setups="sg15", txt=None)

    H2O_gp.set_calculator(gpaw_calc)
    efree_gpaw = H2O_gp.get_potential_energy()
    dft = True

except:
  dft = False



class KnowValues(unittest.TestCase):

  def test_gpaw_vs_siesta_tddft_iter(self):