[gpaw-users] Simple code, yet did not converge, please help

[Ask Hjorth Larsen]

Hi Yuelin

On Fri, 14 Jan 2011, Yuelin Li wrote:

> a very script:
>
>
> from ase import Atoms, Atom
> from gpaw import GPAW
>
> a = 4.  # Size of unit cell (Angstrom)
> c = a / 2
> # Oxygen atom:
> atom1 = Atoms('O',
>              positions=[(c, c, c)],
>              magmoms=[0],
>              cell=(a, a, a))
> # gpaw calculator:
> calc = GPAW(xc='PBE', txt='O.out')
> atom1.set_calculator(calc)
> e1 = atom1.get_potential_energy()
> calc.write('O.gpw')
>
>
> I get the following, please help.
>
>   File "opt1.py", line 14, in <module>
>     e1 = atom1.get_potential_energy()
>   File "/home/ylli/ase/ase/atoms.py", line 503, in get_potential_energy
>     return self.calc.get_potential_energy(self)
>   File "/home/ylli/gpaw/gpaw/aseinterface.py", line 33, in
> get_potential_energy
>     self.calculate(atoms, converge=True)
>   File "/home/ylli/gpaw/gpaw/paw.py", line 272, in calculate
>     raise KohnShamConvergenceError('Did not converge!')
> gpaw.KohnShamConvergenceError: Did not converge!
>
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>

This script performs a spin-paired calculation on an isolated O atom.

You probably want a spin-polarized one, which you can perform by 
specifying hund=True to the calculator (or more generally spinpol=True). 
hund=True will use Hund's rule to establish the initial guess, and will 
also result in a spin-polarized calculation.

Regards
Ask