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from gpaw import GPAW
from ase.calculators.qmmm import EIQMMM, Embedding, LJInteractions
from ase.calculators.tip3p import TIP3P, epsilon0, sigma0
from ase.data import s22
# Create system
atoms = s22.create_s22_system('Water_dimer')
atoms.center(vacuum=4.0)
# Make QM atoms selection of first water molecule:
qm_idx = range(3)
# Set up interaction & embedding object
interaction = LJInteractions({('O', 'O'): (epsilon0, sigma0)})
embedding = Embedding(rc=0.02) # Short range analytical potential cutoff
# Set up calculator
atoms.calc = EIQMMM(
qm_idx,
GPAW(txt='qm.out'),
TIP3P(),
interaction,
embedding=embedding,
vacuum=None, # if None, QM cell = MM cell
output='qmmm.log',
)
print(atoms.get_potential_energy())
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