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# fmt: off
import numpy as np
from ase.build import molecule
from ase.calculators.qmmm import ForceConstantCalculator
from ase.optimize import MDMin
def test_mdmin_maxstep():
atoms = molecule("N2", vacuum=10)
calc = ForceConstantCalculator(np.eye(6) * 100,
atoms.copy(), np.zeros((2, 3)))
atoms.calc = calc
atoms.positions[1] += np.array([1.0, 1.0, 1.0])
initial_positions = atoms.positions.copy()
# Both atoms now have huge forces on them.
# This is a very large dt to force the maxstep clipping to trigger.
opt = MDMin(atoms, dt=1.0)
opt.run(steps=1)
assert np.max(
np.linalg.norm(atoms.positions - initial_positions, axis=1)) <= 0.2
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