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# fmt: off
import pytest
from ase.constraints import FixAtoms
from ase.lattice.cubic import FaceCenteredCubic
from ase.md.velocitydistribution import (
MaxwellBoltzmannDistribution,
Stationary,
ZeroRotation,
)
from ase.units import kB
def test_maxwellboltzmann():
atoms = FaceCenteredCubic(size=(50, 50, 50), symbol="Cu", pbc=False)
print("Number of atoms:", len(atoms))
MaxwellBoltzmannDistribution(atoms, temperature_K=0.1 / kB)
temp = atoms.get_kinetic_energy() / (1.5 * len(atoms))
print("Temperature", temp, " (should be 0.1)")
assert abs(temp - 0.1) < 1e-3
def test_maxwellboltzmann_dof():
atoms = FaceCenteredCubic(size=(50, 50, 50), symbol="Cu", pbc=False)
atoms.set_constraint(FixAtoms(range(250000)))
MaxwellBoltzmannDistribution(atoms, temperature_K=1000)
assert pytest.approx(atoms.get_temperature(), 5) == 1000
MaxwellBoltzmannDistribution(atoms, temperature_K=1000, force_temp=True)
assert pytest.approx(atoms.get_temperature(), 1e-8) == 1000
Stationary(atoms, preserve_temperature=True)
assert pytest.approx(atoms.get_temperature(), 1e-8) == 1000
ZeroRotation(atoms, preserve_temperature=True)
assert pytest.approx(atoms.get_temperature(), 1e-8) == 1000
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