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# fmt: off
from math import pi
import pytest
from numpy.testing import assert_allclose
from ase import Atoms
from ase.units import _e, _eps0 # for reference values only
@pytest.mark.calculator_lite()
@pytest.mark.calculator('lammpsrun')
def test_lammps_units_conversions(factory):
distance = 1.5 # Angstr.
ref_energy = -2 * _e * 1e10 / (4 * pi * _eps0 * distance)
ref_force = 2 * _e * 1e10 / (4 * pi * _eps0 * distance**2)
atoms = Atoms(['H', 'O'], [(0.1, 0.1, 0.1),
(0.1, 0.1, 0.1 + distance)])
atoms.set_initial_charges([1, -2])
atoms.center(10.1)
for units in ['real', 'metal', 'electron', 'nano']:
with factory.calc(
specorder=['H', 'O'],
pair_style='coul/cut 10.0',
pair_coeff=['* *'],
atom_style='charge',
units=units
) as calc:
atoms.calc = calc
energy = atoms.get_potential_energy()
force = atoms.get_forces()[0, 2]
assert_allclose(energy, ref_energy, atol=1e-4, rtol=1e-4)
assert_allclose(force, ref_force, atol=1e-4, rtol=1e-4)
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