[gpaw-users] Large dipol moment

[friedrir at mailserver.tu-freiberg.de]

Dear GPAW users,

when I tried to do some calculations on Au-surfaces using the attached  
input file I got a strange effect in the output. There a very large  
dipol moment of the slab in x and y direction resulted:

Dipole Moment: [  1.89657860e+01   1.09499746e+01   2.15292464e-03]

These large values seemed quite unphysical to me and the values even  
increased when I enlarged the size of the slab and added an adsorbate.  
Could this effect be due to the way the atomic cores of the Au-atoms  
are included in the cell at the left and right boundary when the dipol  
moment is calculated? And is there a solution to get a more reasonable  
dipol moment? Thank you very much in advance.

Rico

from ase import Atoms
from ase.visualize import view
from ase.lattice.surface import *
from ase.lattice.surface import add_adsorbate
from gpaw import GPAW, Mixer, MixerSum, MixerDif, FermiDirac, PoissonSolver
from ase.optimize import QuasiNewton
from ase.parallel import parprint
from ase import io

slab=fcc111('Au', size=(3,3,5), vacuum=8.0)

c = GPAW(
   gpts=(40, 40, 128),
   kpts=(1,1,1),
   mode='lcao',
   basis='dzp',
   xc='PBE',
   mixer=Mixer(),
   occupations=FermiDirac(5e-3),
   maxiter=300,
   poissonsolver=PoissonSolver(relax='GS', eps=1e-12),
   convergence={'energy': 0.0001},
   usesymm=False,
)
slab.set_calculator(c)

relax = QuasiNewton(slab, trajectory='lcao_au111.traj')
relax.run(fmax=0.03)

epot = slab.get_potential_energy()

parprint('Epot: {0}'.format(epot))

c.write('au111.gpw', mode='all')
io.write('au111_rel.cif')

parprint('>>> DONE <<<')