ASE Manual Release 3.6.1.2825 CAMd - CampOS Wiki

from ase.lattice.surface import fcc100, add_adsorbate
from ase.constraints import FixAtoms
from ase.calculators.emt import EMT
from ase.optimize import QuasiNewton
# 2x2-Al(001) surface with 3 layers and an
# Au atom adsorbed in a hollow site:
slab = fcc100(’Al’, size=(2, 2, 3))
add_adsorbate(slab, ’Au’, 1.7, ’hollow’)
slab.center(axis=2, vacuum=4.0)
# Make sure the structure is correct:
#view(slab)
# Fix second and third layers:
mask = [atom.tag > 1 for atom in slab]
#print mask
slab.set_constraint(FixAtoms(mask=mask))
# Use EMT potential:
slab.set_calculator(EMT())
# Initial state:
qn = QuasiNewton(slab, trajectory=’initial.traj’)
qn.run(fmax=0.05)
# Final state:
slab[-1].x += slab.get_cell()[0, 0] / 2
qn = QuasiNewton(slab, trajectory=’final.traj’)
qn.run(fmax=0.05)
Note: Notice how the tags are used to select the constrained atoms
Now, do the NEB calculation:
from ase.io import read
from ase.constraints import FixAtoms
from ase.calculators.emt import EMT
from ase.neb import NEB
from ase.optimize import BFGS
initial = read(’initial.traj’)
final = read(’final.traj’)
constraint = FixAtoms(mask=[atom.tag > 1 for atom in initial])
images = [initial]
for i in range(3):
image = initial.copy()
image.set_calculator(EMT())
image.set_constraint(constraint)
images.append(image)
images.append(final)
neb = NEB(images)
neb.interpolate()
qn = BFGS(neb, trajectory=’neb.traj’)
qn.run(fmax=0.05)
ASE Manual, Release 3.6.1.2828
6.2. ASE 35