All,
I am having trouble with forcefield constraints in OpenBabel regardless of the
potential selected or size of the factor the angle always converges to an
unconstrained minima. See the minimal example with carbon dioxide below:
from openbabel import openbabel
obConversion = openbabel.OBConversion()
obConversion.SetInFormat("smi")
mol = openbabel.OBMol()
obConversion.ReadString(mol, "C(=O)=O")
builder = openbabel.OBBuilder()
builder.Build(mol)
constraints = openbabel.OBFFConstraints()
constraints.AddAngleConstraint(2,1,3,float(178.0))
constraints.SetFactor(1e10)
ff = openbabel.OBForceField.FindForceField("gaff")
ff.Setup(mol, constraints)
ff.ConjugateGradients(10000, 1.0e-6)
ff.GetCoordinates(mol)
print(mol.GetAngle(mol.GetAtom(2),mol.GetAtom(1),mol.GetAtom(3)))
This always converges to:
$ python angle_demo.py
179.9743765482302
Any help would be appreciated. I am running Open Babel 3.1.0
Thanks,
Richard Overstreet
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