from ase import Atoms
from gpaw import GPAW

d = 1.1   # bondlength of CO molecule
a = 5.0   # sidelength of unit cell
c = a / 2
atoms = Atoms('CO',
              positions=[(c - d / 2, c, c),
                         (c + d / 2, c, c)],
              cell=(a, a, a))

calc = GPAW(nbands=5, h=0.2, txt=None)
atoms.set_calculator(calc)

# Start a calculation:
energy = atoms.get_potential_energy()

# Save wave functions:
calc.write('CO.gpw', mode='all')