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import pytest
from ase import io
from ase.build import bulk, molecule
from ase.calculators.emt import EMT
from ase.calculators.vdwcorrection import TS09Polarizability, vdWTkatchenko09prl
# fake objects for the test
class FakeHirshfeldPartitioning:
def __init__(self, calculator):
self.calculator = calculator
def initialize(self):
pass
def get_effective_volume_ratios(self):
return [1] * len(self.calculator.atoms)
def get_calculator(self):
return self.calculator
class FakeDFTcalculator(EMT):
def __init__(self, atoms=None):
self.atoms = atoms
super().__init__()
def get_xc_functional(self):
return 'PBE'
def test_ts09(testdir):
a = 4.05 # Angstrom lattice spacing
al = bulk('Al', 'fcc', a=a)
al = al.repeat([2, 2, 1])
cc = FakeDFTcalculator()
hp = FakeHirshfeldPartitioning(cc)
c = vdWTkatchenko09prl(hp, [3] * len(al))
al.calc = c
al.get_potential_energy()
assert (al.get_potential_energy(force_consistent=False)
== al.get_potential_energy(force_consistent=True))
fname = 'out.traj'
al.write(fname)
# check that the output exists
atoms = io.read(fname)
assert (atoms.get_potential_energy()
== pytest.approx(al.get_potential_energy()))
p = atoms.calc.parameters
assert p['calculator'] == cc.name
assert p['xc'] == cc.get_xc_functional()
assert p['uncorrected_energy'] == pytest.approx(cc.get_potential_energy())
def test_ts09_polarizability(testdir):
atoms = molecule('N2')
cc = FakeDFTcalculator(atoms)
hp = FakeHirshfeldPartitioning(cc)
c = vdWTkatchenko09prl(hp, [2, 2])
atoms.calc = c
# interface to enable Raman calculations
pol = TS09Polarizability()
alpha_cc = pol(atoms)
# polarizability is a tensor
assert alpha_cc.shape == (3, 3)
assert alpha_cc.diagonal() == pytest.approx(0.1523047, .005)
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