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"""Check if we can deal with spin-broken symmetries."""
from numpy import array
import pytest
from ase import Atoms
@pytest.mark.calculator('nwchem')
def test_main(factory):
"""Perform C_{\\inf v} calculation on Cr_2."""
# PBE from
# J. Chem. Phys. 112 , 5576 (2000)
# https://doi.org/10.1063/1.481183
e_literature = -1.34
names = ['Cr2_sp_up.mos',
'Cr2_sp_down.mos']
fragment_energies = array([.0] * 2)
cr_atom = Atoms('Cr', positions=[(0, 0, 0)], pbc=False)
for orientation in range(2): # create two fragments
imm = 6 * (-1)**orientation
cr_atom.set_initial_magnetic_moments([imm])
calc = factory.calc(
task='energy', xc='pbe', theory='dft',
dft=dict(convergence=dict(energy=1e-3,
density=1e-2,
gradient=5e-2),
vectors='input atomic output {}'
.format(names[orientation])),
charge=0,
basis='"DZVP2 (DFT Orbital)"'
)
cr_atom.calc = calc
fragment_energies[orientation] = cr_atom.get_potential_energy()
cr_dimer = Atoms('Cr2', positions=[(0, 0, 0), (0, 0, 1.93)], pbc=False)
cr_dimer.set_initial_magnetic_moments([0, 0])
calc = factory.calc(
task='energy', xc='pbe', theory='dft',
dft=dict(convergence=dict(energy=1e-3,
density=1e-2,
gradient=5e-2),
odft=None,
vectors='input fragment {} output Cr2_AF.mos'
.format(' '.join(names))),
basis='"DZVP2 (DFT Orbital)"',
charge=0
)
cr_dimer.calc = calc
e_dimer = cr_dimer.get_potential_energy()
e_tot = e_dimer - fragment_energies.sum()
assert abs(e_tot - e_literature) < 0.01
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