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from ase.build import fcc100, add_adsorbate
from ase.constraints import FixAtoms
from ase.calculators.emt import EMT
from ase.dimer import DimerControl, MinModeAtoms, MinModeTranslate
def test_dimer_method(testdir):
# Set up a small "slab" with an adatoms
atoms = fcc100('Pt', size=(2, 2, 1), vacuum=10.0)
add_adsorbate(atoms, 'Pt', 1.611, 'hollow')
# Freeze the "slab"
mask = [atom.tag > 0 for atom in atoms]
atoms.set_constraint(FixAtoms(mask=mask))
# Calculate using EMT
atoms.calc = EMT()
atoms.get_potential_energy()
# Set up the dimer
with DimerControl(initial_eigenmode_method='displacement',
displacement_method='vector', logfile=None,
mask=[0, 0, 0, 0, 1]) as d_control:
d_atoms = MinModeAtoms(atoms, d_control)
# Displace the atoms
displacement_vector = [[0.0] * 3] * 5
displacement_vector[-1][1] = -0.1
d_atoms.displace(displacement_vector=displacement_vector)
# Converge to a saddle point
with MinModeTranslate(d_atoms, trajectory='dimer_method.traj',
logfile=None) as dim_rlx:
dim_rlx.run(fmax=0.001)
# Test the results
tolerance = 1e-3
assert(d_atoms.get_barrier_energy() - 1.03733136918 < tolerance)
assert(abs(d_atoms.get_curvature() + 0.900467048707) < tolerance)
assert(d_atoms.get_eigenmode()[-1][1] < -0.99)
assert(abs(d_atoms.get_positions()[-1][1]) < tolerance)
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