RBTorsionForce
¶

class RBTorsionForce : public OpenMM::Force¶
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 call addTorsion() once for each torsion. After a torsion has been added, you can modify its force field parameters by calling setTorsionParameters(). This will have no effect on Contexts that already exist unless you call updateParametersInContext().
Public Functions

RBTorsionForce()¶
Create a RBTorsionForce.

inline 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 this Force object. This method provides an efficient method to update certain parameters in an existing Context without needing to reinitialize it. Simply call setTorsionParameters() to modify this object’s parameters, then call updateParametersInContext() to copy them over to the Context.
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.

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

RBTorsionForce()¶