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 RyckaertBellemans 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
RBTorsionForce
Create a RBTorsionForce
.getNumTorsions
Get the number of RyckaertBellemans torsion terms in the potential function addTorsion
Add a RyckaertBellemans torsion term to the force field. getTorsionParameters
Get the force field parameters for a RyckaertBellemans torsion term. setTorsionParameters
Set the force field parameters for a RyckaertBellemans torsion term. updateParametersInContext
Update the pertorsion parameters in a Context
to match those stored in thisForce
object.setUsesPeriodicBoundaryConditions
Set whether this force should apply periodic boundary conditions when calculating displacements. usesPeriodicBoundaryConditions
Returns whether or not this force makes use of periodic boundary conditions. 
RBTorsionForce
()¶ Create a
RBTorsionForce()
.

int
getNumTorsions
() const¶ Get the number of RyckaertBellemans 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 RyckaertBellemans 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

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 RyckaertBellemans 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

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 RyckaertBellemans 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

void
updateParametersInContext
(Context &context)¶ Update the pertorsion 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 pertorsion parameters. The set of particles involved in a torsion cannot be changed, nor can new torsions be added.

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.

bool
usesPeriodicBoundaryConditions
() const¶ Returns whether or not this force makes use of periodic boundary conditions.
Returns: true if force uses PBC and false otherwise
