RBTorsionForce¶
-
class
OpenMM
::
RBTorsionForce
¶ This class implements an interaction between groups of four particles that varies with the torsion angle between them according to the Ryckaert-Bellemans potential. To use it, create an
RBTorsionForce
object then calladdTorsion()
once for each torsion. After a torsion has been added, you can modify its force field parameters by callingsetTorsionParameters()
. This will have no effect on Contexts that already exist unless you callupdateParametersInContext()
.Methods
Create a
RBTorsionForce
.Get the number of Ryckaert-Bellemans torsion terms in the potential function
Add a Ryckaert-Bellemans torsion term to the force field.
Get the force field parameters for a Ryckaert-Bellemans torsion term.
Set the force field parameters for a Ryckaert-Bellemans torsion term.
Update the per-torsion parameters in a
Context
to match those stored in thisForce
object.Set whether this force should apply periodic boundary conditions when calculating displacements.
Returns whether or not this force makes use of periodic boundary conditions.
-
RBTorsionForce
()¶ Create a
RBTorsionForce()
.
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int
getNumTorsions
() const¶ Get the number of Ryckaert-Bellemans torsion terms in the potential function
-
int
addTorsion
(int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5)¶ Add a Ryckaert-Bellemans torsion term to the force field.
- Parameters
particle1 – the index of the first particle forming the torsion
particle2 – the index of the second particle forming the torsion
particle3 – the index of the third particle forming the torsion
particle4 – the index of the fourth particle forming the torsion
c0 – the coefficient of the constant term, measured in kJ/mol
c1 – the coefficient of the 1st order term, measured in kJ/mol
c2 – the coefficient of the 2nd order term, measured in kJ/mol
c3 – the coefficient of the 3rd order term, measured in kJ/mol
c4 – the coefficient of the 4th order term, measured in kJ/mol
c5 – the coefficient of the 5th order term, measured in kJ/mol
- Returns
the index of the torsion that was added
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void
getTorsionParameters
(int index, int &particle1, int &particle2, int &particle3, int &particle4, double &c0, double &c1, double &c2, double &c3, double &c4, double &c5) const¶ Get the force field parameters for a Ryckaert-Bellemans torsion term.
- Parameters
index – the index of the torsion for which to get parameters
particle1 – [out] the index of the first particle forming the torsion
particle2 – [out] the index of the second particle forming the torsion
particle3 – [out] the index of the third particle forming the torsion
particle4 – [out] the index of the fourth particle forming the torsion
c0 – [out] the coefficient of the constant term, measured in kJ/mol
c1 – [out] the coefficient of the 1st order term, measured in kJ/mol
c2 – [out] the coefficient of the 2nd order term, measured in kJ/mol
c3 – [out] the coefficient of the 3rd order term, measured in kJ/mol
c4 – [out] the coefficient of the 4th order term, measured in kJ/mol
c5 – [out] the coefficient of the 5th order term, measured in kJ/mol
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void
setTorsionParameters
(int index, int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5)¶ Set the force field parameters for a Ryckaert-Bellemans torsion term.
- Parameters
index – the index of the torsion for which to set parameters
particle1 – the index of the first particle forming the torsion
particle2 – the index of the second particle forming the torsion
particle3 – the index of the third particle forming the torsion
particle4 – the index of the fourth particle forming the torsion
c0 – the coefficient of the constant term, measured in kJ/mol
c1 – the coefficient of the 1st order term, measured in kJ/mol
c2 – the coefficient of the 2nd order term, measured in kJ/mol
c3 – the coefficient of the 3rd order term, measured in kJ/mol
c4 – the coefficient of the 4th order term, measured in kJ/mol
c5 – the coefficient of the 5th order term, measured in kJ/mol
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void
updateParametersInContext
(Context &context)¶ Update the per-torsion parameters in a
Context
to match those stored in thisForce
object. This method provides an efficient method to update certain parameters in an existingContext
without needing to reinitialize it. Simply callsetTorsionParameters()
to modify this object’s parameters, then callupdateParametersInContext()
to copy them over to theContext
.The only information this method updates is the values of per-torsion parameters. The set of particles involved in a torsion cannot be changed, nor can new torsions be added.
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void
setUsesPeriodicBoundaryConditions
(bool periodic)¶ Set whether this force should apply periodic boundary conditions when calculating displacements. Usually this is not appropriate for bonded forces, but there are situations when it can be useful.
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bool
usesPeriodicBoundaryConditions
() const¶ Returns whether or not this force makes use of periodic boundary conditions.
- Returns
true if force uses PBC and false otherwise
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