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'''These tests ensure that the potentiostat can keep a sysytem near the PEC'''
import pytest
from ase.build import bulk
from ase.md.velocitydistribution import MaxwellBoltzmannDistribution
from ase.md.contour_exploration import ContourExploration
import numpy as np
from ase.calculators.emt import EMT
from .test_ce_curvature import Al_atom_pair
def Al_block():
size = 2
atoms = bulk('Al', 'fcc', cubic=True).repeat((size, size, size))
atoms.calc = EMT()
return atoms
bulk_Al_settings = {
'maxstep': 1.0,
'parallel_drift': 0.05,
'remove_translation': True,
'potentiostat_step_scale': None,
'use_frenet_serret': True,
'angle_limit': 20,
'loginterval': 1}
def test_potentiostat(testdir):
'''This is very realistic and stringent test of the potentiostatic accuracy
with 32 atoms at ~235 meV/atom above the ground state.'''
name = 'test_potentiostat'
seed = 19460926
atoms = Al_block()
E0 = atoms.get_potential_energy()
atoms.rattle(stdev=0.18, seed=seed)
initial_energy = atoms.get_potential_energy()
rng = np.random.RandomState(seed)
MaxwellBoltzmannDistribution(atoms, temperature_K=300, rng=rng)
with ContourExploration(
atoms,
**bulk_Al_settings,
energy_target=initial_energy,
rng=rng,
trajectory=name + '.traj',
logfile=name + '.log',
) as dyn:
print("Energy Above Ground State: {: .4f} eV/atom".format(
(initial_energy - E0) / len(atoms)))
for i in range(5):
dyn.run(5)
energy_error = (atoms.get_potential_energy() -
initial_energy) / len(atoms)
print('Potentiostat Error {: .4f} eV/atom'.format(energy_error))
assert 0 == pytest.approx(energy_error, abs=0.01)
def test_potentiostat_no_fs(testdir):
'''This test ensures that the potentiostat is working even when curvature
extrapolation (use_fs) is turned off.'''
name = 'test_potentiostat_no_fs'
atoms = Al_atom_pair()
atoms.set_momenta([[0, -1, 0], [0, 1, 0]])
initial_energy = atoms.get_potential_energy()
with ContourExploration(
atoms,
maxstep=0.2,
parallel_drift=0.0,
remove_translation=False,
energy_target=initial_energy,
potentiostat_step_scale=None,
use_frenet_serret=False,
trajectory=name + '.traj',
logfile=name + '.log',
) as dyn:
for i in range(5):
dyn.run(10)
energy_error = (atoms.get_potential_energy() -
initial_energy) / len(atoms)
print('Potentiostat Error {: .4f} eV/atom'.format(energy_error))
assert 0 == pytest.approx(energy_error, abs=0.01)
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