>>> from ase import Atoms
>>> from ase.optimize import BFGS
>>> from ase.calculators.nwchem import NWChem
>>> from ase.io import write
>>> h2 = Atoms('H2',
...            positions=[[0, 0, 0],
...                       [0, 0, 0.7]])
...
>>> h2.calc = NWChem(xc='PBE')
>>> opt = BFGS(h2)
>>> opt.run(fmax=0.02)
BFGS:   0  19:10:49    -31.435229     2.2691
BFGS:   1  19:10:50    -31.490773     0.3740
BFGS:   2  19:10:50    -31.492791     0.0630
BFGS:   3  19:10:51    -31.492848     0.0023
>>> write('H2.xyz', h2)
>>> h2.get_potential_energy()
-31.492847800329216