PeriodicTorsionForce Class Reference

This class implements an interaction between groups of four particles that varies periodically with the torsion angle between them. More...

#include <PeriodicTorsionForce.h>

Inheritance diagram for PeriodicTorsionForce:

Public Member Functions
	PeriodicTorsionForce ()
	Create a PeriodicTorsionForce. More...
int	getNumTorsions () const
	Get the number of periodic torsion terms in the potential function. More...
int	addTorsion (int particle1, int particle2, int particle3, int particle4, int periodicity, double phase, double k)
	Add a periodic torsion term to the force field. More...
void	getTorsionParameters (int index, int &particle1, int &particle2, int &particle3, int &particle4, int &periodicity, double &phase, double &k) const
	Get the force field parameters for a periodic torsion term. More...
void	setTorsionParameters (int index, int particle1, int particle2, int particle3, int particle4, int periodicity, double phase, double k)
	Set the force field parameters for a periodic torsion term. More...
void	updateParametersInContext (Context &context)
	Update the per-torsion parameters in a Context to match those stored in this Force object. More...
bool	usesPeriodicBoundaryConditions () const
	Returns whether or not this force makes use of periodic boundary conditions. More...
Public Member Functions inherited from Force
	Force ()
virtual	~Force ()
int	getForceGroup () const
	Get the force group this Force belongs to. More...
void	setForceGroup (int group)
	Set the force group this Force belongs to. More...

Protected Member Functions
ForceImpl *	createImpl () const
	When a Context is created, it invokes this method on each Force in the System. More...
Protected Member Functions inherited from Force
ForceImpl &	getImplInContext (Context &context)
	Get the ForceImpl corresponding to this Force in a Context. More...
ContextImpl &	getContextImpl (Context &context)
	Get the ContextImpl corresponding to a Context. More...

Detailed Description

This class implements an interaction between groups of four particles that varies periodically with the torsion angle between them.

To use it, create a PeriodicTorsionForce 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().

Constructor & Destructor Documentation

PeriodicTorsionForce

(

)

Create a PeriodicTorsionForce.

Member Function Documentation

int addTorsion	(	int	particle1,
		int	particle2,
		int	particle3,
		int	particle4,
		int	periodicity,
		double	phase,
		double	k
	)

Add a periodic 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
periodicity	the periodicity of the torsion
phase	the phase offset of the torsion, measured in radians
k	the force constant for the torsion

Returns

the index of the torsion that was added

ForceImpl* createImpl ( ) const

protectedvirtual

When a Context is created, it invokes this method on each Force in the System.

It should create a new ForceImpl object which can be used by the context for calculating forces. The ForceImpl will be deleted automatically when the Context is deleted.

Implements Force.

int getNumTorsions ( ) const

inline

Get the number of periodic torsion terms in the potential function.

void getTorsionParameters	(	int	index,
		int &	particle1,
		int &	particle2,
		int &	particle3,
		int &	particle4,
		int &	periodicity,
		double &	phase,
		double &	k
	)		const

Get the force field parameters for a periodic torsion term.

Parameters

index	the index of the torsion for which to get 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
periodicity	the periodicity of the torsion
phase	the phase offset of the torsion, measured in radians
k	the force constant for the torsion

void setTorsionParameters	(	int	index,
		int	particle1,
		int	particle2,
		int	particle3,
		int	particle4,
		int	periodicity,
		double	phase,
		double	k
	)

Set the force field parameters for a periodic 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
periodicity	the periodicity of the torsion
phase	the phase offset of the torsion, measured in radians
k	the force constant for the torsion

void updateParametersInContext

(

Context &

context

)

Update the per-torsion 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 per-torsion parameters. The set of particles involved in a torsion cannot be changed, nor can new torsions be added.

bool usesPeriodicBoundaryConditions ( ) const

inlinevirtual

Returns whether or not this force makes use of periodic boundary conditions.

Returns

true if force uses PBC and false otherwise

Reimplemented from Force.

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The documentation for this class was generated from the following file:

• PeriodicTorsionForce.h