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import numpy as np
from ase.units import GPa
from ase.build import bulk
from ase.calculators.test import gradient_test
from ase.calculators.lj import LennardJones
from ase.constraints import UnitCellFilter, ExpCellFilter
from ase.optimize import FIRE, LBFGSLineSearch
a0 = bulk('Cu', cubic=True)
# perturb the atoms
s = a0.get_scaled_positions()
s[:, 0] *= 0.995
a0.set_scaled_positions(s)
# perturb the cell
a0.cell[...] += np.random.uniform(-1e-2, 1e-2,
size=9).reshape((3,3))
atoms = a0.copy()
atoms.set_calculator(LennardJones())
ucf = UnitCellFilter(atoms, scalar_pressure=10.0*GPa)
# test all deritatives
f, fn = gradient_test(ucf)
assert abs(f - fn).max() < 1e-6
opt = FIRE(ucf)
opt.run(1e-3)
# check pressure is within 0.1 GPa of target
sigma = atoms.get_stress()/GPa
pressure = -(sigma[0] + sigma[1] + sigma[2])/3.0
assert abs(pressure - 10.0) < 0.1
atoms = a0.copy()
atoms.set_calculator(LennardJones())
ecf = ExpCellFilter(atoms, scalar_pressure=10.0*GPa)
# test all deritatives
f, fn = gradient_test(ecf)
assert abs(f - fn).max() < 1e-6
opt = LBFGSLineSearch(ecf)
opt.run(1e-3)
# check pressure is within 0.1 GPa of target
sigma = atoms.get_stress()/GPa
pressure = -(sigma[0] + sigma[1] + sigma[2])/3.0
assert abs(pressure - 10.0) < 0.1
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