def test_from_toolkit_packmol_boxes(self, pdb_path, unique_molecules):
"""
Test loading some pre-prepared PACKMOL-generated systems.
These use PDB files already prepared in the toolkit because PDB files are a pain.
"""
ff = ForceField("openff-1.0.0.offxml")
pdb_file_path = get_data_file_path("systems/packmol_boxes/" + pdb_path)
pdbfile = openmm.app.PDBFile(pdb_file_path)
top = Topology.from_openmm(
pdbfile.topology,
unique_molecules=unique_molecules,
)
box = pdbfile.topology.getPeriodicBoxVectors()
box = box.value_in_unit(nm) * unit.nanometer
out = ff.create_openff_system(top)
out.box = box
out.positions = pdbfile.getPositions()
assert np.allclose(
out.positions.to(unit.nanometer).magnitude,
pdbfile.getPositions().value_in_unit(nm),
)
get_openmm_energies(out, hard_cutoff=True).compare(
_get_openmm_energies(
omm_sys=ff.create_openmm_system(top),
box_vectors=pdbfile.topology.getPeriodicBoxVectors(),
positions=pdbfile.getPositions(),
hard_cutoff=True,
))
def test_from_openmm_pdbfile(self, argon_ff, argon_top):
pdb_file_path = get_test_file_path("10-argons.pdb")
pdbfile = openmm.app.PDBFile(pdb_file_path)
mol = Molecule.from_smiles("[#18]")
top = Topology.from_openmm(pdbfile.topology, unique_molecules=[mol])
box = pdbfile.topology.getPeriodicBoxVectors()
box = box.value_in_unit(nm) * unit.nanometer
out = argon_ff.create_openff_system(top)
out.box = box
out.positions = pdbfile.getPositions()
assert np.allclose(
out.positions.to(unit.nanometer).magnitude,
pdbfile.getPositions().value_in_unit(nm),
)
get_openmm_energies(out, hard_cutoff=True).compare(
_get_openmm_energies(
omm_sys=argon_ff.create_openmm_system(top),
box_vectors=pdbfile.topology.getPeriodicBoxVectors(),
positions=pdbfile.getPositions(),
hard_cutoff=True,
))
def test_to_lammps_single_mols(mol, n_mols):
"""
Test that ForceField.create_openmm_system and System.to_openmm produce
objects with similar energies
TODO: Tighten tolerances
TODO: Test periodic and non-periodic
"""
parsley = ForceField("openff_unconstrained-1.0.0.offxml")
mol = Molecule.from_smiles(mol)
mol.generate_conformers(n_conformers=1)
top = Topology.from_molecules(n_mols * [mol])
mol.conformers[0] -= np.min(mol.conformers) * omm_unit.angstrom
top.box_vectors = np.eye(3) * np.asarray([10, 10, 10]) * omm_unit.nanometer
if n_mols == 1:
positions = mol.conformers[0]
elif n_mols == 2:
positions = np.vstack(
[mol.conformers[0], mol.conformers[0] + 3 * omm_unit.nanometer]
)
positions = positions * omm_unit.angstrom
openff_sys = parsley.create_openff_system(topology=top)
openff_sys.positions = positions.value_in_unit(omm_unit.nanometer)
openff_sys.box = top.box_vectors
reference = get_openmm_energies(
off_sys=openff_sys, round_positions=3, electrostatics=False
)
lmp_energies = get_lammps_energies(
off_sys=openff_sys, round_positions=3, electrostatics=False
)
_write_lammps_input(
off_sys=openff_sys,
file_name="tmp.in",
electrostatics=False,
)
lmp_energies.compare(
reference,
custom_tolerances={
"Nonbonded": 999 * omm_unit.kilojoule_per_mole,
"Torsion": 0.005 * omm_unit.kilojoule_per_mole,
},
)
def test_argon_buck():
mol = Molecule.from_smiles("[#18]")
top = Topology.from_molecules([mol, mol])
A = 1.69e-8 * unit.Unit("erg / mol") * Avogadro
B = 1 / (0.273 * unit.angstrom)
C = 102e-12 * unit.Unit("erg / mol") * unit.angstrom**6 * Avogadro
A = A.to(unit.Unit("kilojoule/mol"))
B = B.to(unit.Unit("1 / nanometer"))
C = C.to(unit.Unit("kilojoule / mol * nanometer ** 6"))
r = 0.3 * unit.nanometer
buck = BuckinghamvdWHandler()
coul = ElectrostaticsMetaHandler() # Just to pass compatibility checks
pot_key = PotentialKey(id="[#18]")
pot = Potential(parameters={"A": A, "B": B, "C": C})
for top_atom in top.topology_atoms:
top_key = TopologyKey(atom_indices=(top_atom.topology_atom_index, ))
buck.slot_map.update({top_key: pot_key})
coul.charges.update({top_key: 0 * unit.elementary_charge})
buck.potentials[pot_key] = pot
from openff.system.components.system import System
out = System()
out.handlers["Buckingham-6"] = buck
out.handlers["Electrostatics"] = coul
out.topology = top
out.box = [10, 10, 10] * unit.nanometer
out.positions = [[0, 0, 0], [0.3, 0, 0]] * unit.nanometer
out.to_gro("out.gro", writer="internal")
out.to_top("out.top", writer="internal")
gmx_energies = get_gromacs_energies(out, mdp="cutoff_buck")
omm_energies = get_openmm_energies(out)
by_hand = A * exp(-B * r) - C * r**-6
gmx_energies.compare(omm_energies)
resid = simtk_to_pint(gmx_energies.energies["Nonbonded"]) - by_hand
assert resid < 1e-5 * unit.kilojoule / unit.mol
def test_argon(n_mol):
from openff.system.utils import get_test_file_path
ar_ff = ForceField(get_test_file_path("argon.offxml"))
mol = Molecule.from_smiles("[#18]")
mol.add_conformer(np.array([[0, 0, 0]]) * omm_unit.angstrom)
mol.name = "FOO"
top = Topology.from_molecules(n_mol * [mol])
off_sys = ar_ff.create_openff_system(top)
mol.to_file("out.xyz", file_format="xyz")
compound: mb.Compound = mb.load("out.xyz")
packed_box: mb.Compound = mb.fill_box(
compound=compound,
n_compounds=[n_mol],
box=mb.Box([4, 4, 4]),
)
positions = packed_box.xyz * unit.nanometer
positions = np.round(positions, 3)
off_sys.positions = positions
box = np.asarray(packed_box.box.lengths) * unit.nanometer
off_sys.box = box
omm_energies = get_openmm_energies(
off_sys, round_positions=8, hard_cutoff=True, electrostatics=False
)
gmx_energies = get_gromacs_energies(
off_sys, writer="internal", electrostatics=False
)
lmp_energies = get_lammps_energies(off_sys)
omm_energies.compare(lmp_energies)
omm_energies.compare(
gmx_energies,
custom_tolerances={
"Nonbonded": 2e-5 * omm_unit.kilojoule_per_mole,
},
)
def test_water_dimer():
from openff.system.utils import get_test_file_path
tip3p = ForceField(get_test_file_path("tip3p.offxml"))
water = Molecule.from_smiles("O")
top = Topology.from_molecules(2 * [water])
pdbfile = openmm.app.PDBFile(get_test_file_path("water-dimer.pdb"))
positions = np.array(pdbfile.positions / omm_unit.nanometer) * unit.nanometer
openff_sys = tip3p.create_openff_system(top)
openff_sys.positions = positions
openff_sys.box = [10, 10, 10] * unit.nanometer
omm_energies = get_openmm_energies(
openff_sys,
hard_cutoff=True,
electrostatics=False,
)
toolkit_energies = _get_openmm_energies(
tip3p.create_openmm_system(top),
openff_sys.box,
openff_sys.positions,
hard_cutoff=True,
electrostatics=False,
)
omm_energies.compare(toolkit_energies)
# TODO: Fix GROMACS energies by handling SETTLE constraints
# gmx_energies, _ = get_gromacs_energies(openff_sys)
# compare_gromacs_openmm(omm_energies=omm_energies, gmx_energies=gmx_energies)
lmp_energies = get_lammps_energies(openff_sys, electrostatics=False)
lmp_energies.compare(omm_energies)
def test_energies_single_mol(constrained, n_mol, mol_smi):
mol = Molecule.from_smiles(mol_smi)
mol.generate_conformers(n_conformers=1)
mol.name = "FOO"
top = Topology.from_molecules(n_mol * [mol])
if constrained:
parsley = ForceField("openff-1.0.0.offxml")
else:
parsley = ForceField("openff_unconstrained-1.0.0.offxml")
off_sys = parsley.create_openff_system(top)
mol.to_file("out.xyz", file_format="xyz")
compound: mb.Compound = mb.load("out.xyz")
packed_box: mb.Compound = mb.fill_box(
compound=compound,
n_compounds=[n_mol],
density=500, # kg/m^3
)
positions = packed_box.xyz * unit.nanometer
off_sys.positions = positions
box = np.asarray(packed_box.box.lengths) * unit.nanometer
if np.any(box < 4 * unit.nanometer):
off_sys.box = np.array([4, 4, 4]) * unit.nanometer
else:
off_sys.box = box
# Compare directly to toolkit's reference implementation
omm_energies = get_openmm_energies(
off_sys, round_positions=8, hard_cutoff=True, electrostatics=False
)
omm_reference = parsley.create_openmm_system(top)
reference_energies = _get_openmm_energies(
omm_sys=omm_reference,
box_vectors=off_sys.box,
positions=off_sys.positions,
round_positions=8,
hard_cutoff=True,
electrostatics=False,
)
try:
omm_energies.compare(reference_energies)
except EnergyError as e:
if "Nonbonded" in str(e):
# If nonbonded energies differ, at least ensure that the nonbonded
# parameters on each particle match
from openff.system.tests.utils import (
_get_charges_from_openmm_system,
_get_lj_params_from_openmm_system,
)
else:
raise e
omm_sys = off_sys.to_openmm()
np.testing.assert_equal(
np.asarray([*_get_charges_from_openmm_system(omm_sys)]),
np.asarray([*_get_charges_from_openmm_system(omm_reference)]),
)
np.testing.assert_equal(
np.asarray([*_get_lj_params_from_openmm_system(omm_sys)]),
np.asarray([*_get_lj_params_from_openmm_system(omm_reference)]),
)
mdp = "cutoff_hbonds" if constrained else "cutoff"
# Compare GROMACS writer and OpenMM export
gmx_energies = get_gromacs_energies(off_sys, mdp=mdp, electrostatics=False)
custom_tolerances = {
"Bond": 2e-5 * n_mol * omm_unit.kilojoule_per_mole,
"Nonbonded": 1e-3 * n_mol * omm_unit.kilojoule_per_mole,
}
if constrained:
# GROMACS might use the initial bond lengths, not the equilibrium bond lengths,
# in the initial configuration, making angles differ slightly
custom_tolerances.update(
{
"Angle": 5e-2 * n_mol * omm_unit.kilojoule_per_mole,
"Nonbonded": 2.0 * n_mol * omm_unit.kilojoule_per_mole,
}
)
gmx_energies.compare(
omm_energies,
custom_tolerances=custom_tolerances,
)
if not constrained:
other_energies = get_openmm_energies(
off_sys,
round_positions=8,
hard_cutoff=True,
electrostatics=True,
)
lmp_energies = get_lammps_energies(off_sys)
custom_tolerances = {
"Nonbonded": 0.5 * n_mol * omm_unit.kilojoule_per_mole,
}
lmp_energies.compare(other_energies, custom_tolerances=custom_tolerances)
def test_packmol_boxes(toolkit_file_path):
# TODO: Isolate a set of systems here instead of using toolkit data
# TODO: Fix nonbonded energy differences
from openff.toolkit.utils import get_data_file_path
pdb_file_path = get_data_file_path(toolkit_file_path)
pdbfile = openmm.app.PDBFile(pdb_file_path)
ethanol = Molecule.from_smiles("CCO")
cyclohexane = Molecule.from_smiles("C1CCCCC1")
omm_topology = pdbfile.topology
off_topology = Topology.from_openmm(
omm_topology, unique_molecules=[ethanol, cyclohexane]
)
parsley = ForceField("openff_unconstrained-1.0.0.offxml")
off_sys = parsley.create_openff_system(off_topology)
off_sys.box = np.asarray(
pdbfile.topology.getPeriodicBoxVectors() / omm_unit.nanometer,
)
off_sys.positions = np.asarray(
pdbfile.positions / omm_unit.nanometer,
)
sys_from_toolkit = parsley.create_openmm_system(off_topology)
omm_energies = get_openmm_energies(off_sys, hard_cutoff=True, electrostatics=False)
reference = _get_openmm_energies(
sys_from_toolkit,
off_sys.box,
off_sys.positions,
hard_cutoff=True,
electrostatics=False,
)
omm_energies.compare(
reference,
custom_tolerances={
"Nonbonded": 2e-2 * omm_unit.kilojoule_per_mole,
},
)
# custom_tolerances={"HarmonicBondForce": 1.0}
# Compare GROMACS writer and OpenMM export
gmx_energies = get_gromacs_energies(off_sys, electrostatics=False)
omm_energies_rounded = get_openmm_energies(
off_sys,
round_positions=8,
hard_cutoff=True,
electrostatics=False,
)
omm_energies_rounded.compare(
other=gmx_energies,
custom_tolerances={
"Angle": 1e-2 * omm_unit.kilojoule_per_mole,
"Torsion": 1e-2 * omm_unit.kilojoule_per_mole,
"Nonbonded": 3200 * omm_unit.kilojoule_per_mole,
},
)
def test_ethanol_opls():
mol = Molecule.from_smiles("CC")
mol.generate_conformers(n_conformers=1)
top = mol.to_topology()
parsley = ForceField("openff-1.0.0.offxml")
out = parsley.create_openff_system(top)
out.box = [4, 4, 4]
out.positions = mol.conformers[0]
out.positions = np.round(out.positions, 2)
rb_torsions = RBTorsionHandler()
smirks = "[#1:1]-[#6X4:2]-[#6X4:3]-[#1:4]"
pot_key = PotentialKey(id=smirks)
for proper in top.propers:
top_key = TopologyKey(atom_indices=tuple(a.topology_atom_index
for a in proper))
rb_torsions.slot_map.update({top_key: pot_key})
# Values from HC-CT-CT-HC RB torsion
# https://github.com/mosdef-hub/foyer/blob/7816bf53a127502520a18d76c81510f96adfdbed/foyer/forcefields/xml/oplsaa.xml#L2585
pot = Potential(
parameters={
"c0": 0.6276 * kj_mol,
"c1": 1.8828 * kj_mol,
"c2": 0.0 * kj_mol,
"c3": -2.5104 * kj_mol,
"c4": 0.0 * kj_mol,
"c5": 0.0 * kj_mol,
})
rb_torsions.potentials.update({pot_key: pot})
out.handlers.update({"RBTorsions": rb_torsions})
out.handlers.pop("ProperTorsions")
gmx = get_openmm_energies(out, round_positions=3).energies["Torsion"]
omm = get_gromacs_energies(out).energies["Torsion"]
assert (gmx - omm).value_in_unit(omm_unit.kilojoule_per_mole) < 1e-3
# Given that these force constants are copied from Foyer's OPLS-AA file,
# compare to processing through the current MoSDeF pipeline
try:
import foyer
import mbuild
except ModuleNotFoundError:
return
comp = mbuild.load("CC", smiles=True)
comp.xyz = mol.conformers[0].value_in_unit(omm_unit.nanometer)
ff = foyer.Forcefield(name="oplsaa")
from_foyer = ff.apply(comp)
from_foyer.box = [40, 40, 40, 90, 90, 90]
from_foyer.save("from_foyer.top")
from_foyer.save("from_foyer.gro")
rb_torsion_energy_from_foyer = run_gmx_energy(
top_file="from_foyer.top",
gro_file="from_foyer.gro",
mdp_file=get_mdp_file("default"),
).energies["Torsion"]
assert (omm - rb_torsion_energy_from_foyer).value_in_unit(
omm_unit.kilojoule_per_mole) < 1e-3
