[gpaw-users] Spin Polarized Calculations

[Michael F. Peintinger]

Hi Rolf,

thank you for your answer. It helped me a lot.

I did the following:

mm = [0]*NAtoms
for i in range (40,43):
  for j in range (i+1,43):
    # 2 unpaired electrons in the molecule for triplet state
    mm[i] = 1.0 # one unpaired electron at i
    mm[j] = 1.0 # one unpaired electron at j
    structure.set_initial_magnetic_moments(mm)
    calc = GPAW( h=0.2, xc='PBE', charge=2, spinpol=True )
    structure.set_calculator( calc )
    E_PBE = structure.get_potential_energy()
    # reset mm
    mm[i] = 0.0
    mm[j] = 0.0

The resulting energies are almost degenerate. I guess it is about
accuracy now. 

Thank you for the tip.


On Fri, 2010-07-16 at 00:43 +0200, Rolf Wuerdemann wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
> 
> Michael F. Peintinger schrieb:
> > Dear all,
> 
> Hi Michael,
> > 
> > how do i perform a spin polarized calculation with fixes spin.
> > 
> > I need to calculate the energy difference between singlet and triplet
> > state.
> > 
> > Is there a way to set that there are two unpaired electrons in the
> > system?
> 
> I would try to set the initial magnetic moments and afterwards
> "fixmagmom=true" in the calculator:
> 
> <code snippet>
> nratoms=len(s)           # say we have two here
> mm = [0] * nratoms	# setup some array
> mm[0] = 1.0		# set the magnetic moment according
> mm[1] = 1.0		# to your system, two unpaired e-
> s.set_initial_magnetic_moments(mm)	# s is our ase-atoms object
> c = GPAW(_some_options,
>         occupations=FermiDirac(width=0.1, fixmagmom=True),
>          _some_more_options)
> s.set_calculator(c)			# have some fun
> </code snippet>
> 
> But be aware - gpaw will calculate _two_ fermi levels in this
> case (one for each spin)
> > 
> > Regards
> > 
> > 
> > Michael
> > 
> Hope this fits your needs,
> 
>   kind regards,
> 
>       Rolf
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-- 
Dipl. Chem. Michael F. Peintinger

Institute of Physical and
Theoretical Chemistry

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