def __init__(self, symbol):
self.__symbol = symbol
bond_length = {'O': 1.21}[symbol]
atoms = Atoms(symbol*2, positions=[[0,-bond_length/2., 0], [0, bond_length/2., 0]],
cell=(10, 10, 10+bond_length)
)
atoms.set_initial_magnetic_moments([1,1])
Molecule.__init__(self, atoms)
