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import ase
from ase.calculators.lj import LennardJones
from ase.constraints import FixBondLength
from ase.optimize import FIRE
for wrap in [False, True]:
a = ase.Atoms('CCC',
positions=[[1, 0, 5],
[0, 1, 5],
[-1, 0.5, 5]],
cell=[10, 10, 10],
pbc=True)
if wrap:
a.set_scaled_positions(a.get_scaled_positions() % 1.0)
a.set_calculator(LennardJones())
a.set_constraint(FixBondLength(0, 2))
d1 = a.get_distance(0, 2, mic=True)
FIRE(a, logfile=None).run(fmax=0.01)
e = a.get_potential_energy()
d2 = a.get_distance(0, 2, mic=True)
assert abs(e - -2.034988) < 1e-6
assert abs(d1 - d2) < 1e-6
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