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import pytest
from ase.build import diamond100
from ase.optimize import BFGS
from ase.constraints import FixAtoms
@pytest.mark.calculator_lite
@pytest.mark.calculator('dftb')
def test_dftb_relax_surface(factory):
calc = factory.calc(
label='dftb',
kpts=(2, 2, 1),
Hamiltonian_SCC='Yes',
Hamiltonian_Filling='Fermi {',
Hamiltonian_Filling_empty='Temperature [Kelvin] = 500.0',
)
a = 5.40632280995384
atoms = diamond100('Si', (1, 1, 6), a=a, vacuum=6., orthogonal=True,
periodic=True)
atoms.positions[-2:,2] -= 0.2
atoms.set_constraint(FixAtoms(indices=range(4)))
atoms.calc = calc
dyn = BFGS(atoms, logfile='-')
dyn.run(fmax=0.1)
e = atoms.get_potential_energy()
assert abs(e - -214.036907) < 1., e
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