DrudeForce Class Reference

This class implements forces that are specific to Drude oscillators. More...

#include <DrudeForce.h>

Inheritance diagram for DrudeForce:

Public Member Functions
	DrudeForce ()
	Create a DrudeForce. More...
int	getNumParticles () const
	Get the number of particles for which force field parameters have been defined. More...
int	getNumScreenedPairs () const
	Get the number of special interactions that should be calculated differently from other interactions. More...
int	addParticle (int particle, int particle1, int particle2, int particle3, int particle4, double charge, double polarizability, double aniso12, double aniso34)
	Add a Drude particle to which forces should be applied. More...
void	getParticleParameters (int index, int &particle, int &particle1, int &particle2, int &particle3, int &particle4, double &charge, double &polarizability, double &aniso12, double &aniso34) const
	Get the parameters for a Drude particle. More...
void	setParticleParameters (int index, int particle, int particle1, int particle2, int particle3, int particle4, double charge, double polarizability, double aniso12, double aniso34)
	Set the parameters for a Drude particle. More...
int	addScreenedPair (int particle1, int particle2, double thole)
	Add an interaction to the list of screened pairs. More...
void	getScreenedPairParameters (int index, int &particle1, int &particle2, double &thole) const
	Get the force field parameters for screened pair. More...
void	setScreenedPairParameters (int index, int particle1, int particle2, double thole)
	Set the force field parameters for screened pair. More...
void	updateParametersInContext (Context &context)
	Update the particle and screened pair parameters in a Context to match those stored in this Force object. 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 forces that are specific to Drude oscillators.

There are two distinct forces it applies: an anisotropic harmonic force connecting each Drude particle to its parent particle; and a screened Coulomb interaction between specific pairs of dipoles. The latter is typically used between closely bonded particles whose Coulomb interaction would otherwise be fully excluded.

To use this class, create a DrudeForce object, then call addParticle() once for each Drude particle in the System to define its parameters. After a particle has been added, you can modify its force field parameters by calling setParticleParameters(). This will have no effect on Contexts that already exist unless you call updateParametersInContext(). Likewise, call addScreenedPair() for each pair of dipoles (each dipole consisting of a Drude particle and its parent) that should be computed.

Constructor & Destructor Documentation

DrudeForce

(

)

Create a DrudeForce.

Member Function Documentation

int addParticle	(	int	particle,
		int	particle1,
		int	particle2,
		int	particle3,
		int	particle4,
		double	charge,
		double	polarizability,
		double	aniso12,
		double	aniso34
	)

Add a Drude particle to which forces should be applied.

Parameters

particle	the index within the System of the Drude particle
particle1	the index within the System of the particle to which the Drude particle is attached
particle2	the index within the System of the second particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso12 will be ignored.
particle3	the index within the System of the third particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
particle4	the index within the System of the fourth particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
charge	The charge on the Drude particle
polarizability	The isotropic polarizability
aniso12	The scale factor for the polarizability along the direction defined by particle1 and particle2
aniso34	The scale factor for the polarizability along the direction defined by particle3 and particle4

Returns

the index of the particle that was added

int addScreenedPair	(	int	particle1,
		int	particle2,
		double	thole
	)

Add an interaction to the list of screened pairs.

Parameters

particle1	the index within this Force of the first particle involved in the interaction
particle2	the index within this Force of the second particle involved in the interaction
thole	the Thole screening factor

Returns

the index of the screenedPair 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 getNumParticles ( ) const

inline

Get the number of particles for which force field parameters have been defined.

int getNumScreenedPairs ( ) const

inline

Get the number of special interactions that should be calculated differently from other interactions.

void getParticleParameters	(	int	index,
		int &	particle,
		int &	particle1,
		int &	particle2,
		int &	particle3,
		int &	particle4,
		double &	charge,
		double &	polarizability,
		double &	aniso12,
		double &	aniso34
	)		const

Get the parameters for a Drude particle.

Parameters

index	the index of the Drude particle for which to get parameters
particle	the index within the System of the Drude particle
particle1	the index within the System of the particle to which the Drude particle is attached
particle2	the index within the System of the second particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso12 will be ignored.
particle3	the index within the System of the third particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
particle4	the index within the System of the fourth particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
charge	The charge on the Drude particle
polarizability	The isotropic polarizability
aniso12	The scale factor for the polarizability along the direction defined by particle1 and particle2
aniso34	The scale factor for the polarizability along the direction defined by particle3 and particle4

void getScreenedPairParameters	(	int	index,
		int &	particle1,
		int &	particle2,
		double &	thole
	)		const

Get the force field parameters for screened pair.

Parameters

index	the index of the pair for which to get parameters
particle1	the index within this Force of the first particle involved in the interaction
particle2	the index within this Force of the second particle involved in the interaction
thole	the Thole screening factor

void setParticleParameters	(	int	index,
		int	particle,
		int	particle1,
		int	particle2,
		int	particle3,
		int	particle4,
		double	charge,
		double	polarizability,
		double	aniso12,
		double	aniso34
	)

Set the parameters for a Drude particle.

Parameters

index	the index of the Drude particle for which to set parameters
particle	the index within the System of the Drude particle
particle1	the index within the System of the particle to which the Drude particle is attached
particle2	the index within the System of the second particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso12 will be ignored.
particle3	the index within the System of the third particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
particle4	the index within the System of the fourth particle used for defining anisotropic polarizability. This may be set to -1, in which case aniso34 will be ignored.
charge	The charge on the Drude particle
polarizability	The isotropic polarizability
aniso12	The scale factor for the polarizability along the direction defined by particle1 and particle2
aniso34	The scale factor for the polarizability along the direction defined by particle3 and particle4

void setScreenedPairParameters	(	int	index,
		int	particle1,
		int	particle2,
		double	thole
	)

Set the force field parameters for screened pair.

Parameters

index	the index of the pair for which to get parameters
particle1	the index within this Force of the first particle involved in the interaction
particle2	the index within this Force of the second particle involved in the interaction
thole	the Thole screening factor

void updateParametersInContext

(

Context &

context

)

Update the particle and screened pair 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 setParticleParameters() and setScreenedPairParameters() to modify this object's parameters, then call updateParametersInContext() to copy them over to the Context.

This method has several limitations. It can be used to modify the numeric parameters associated with a particle or screened pair (polarizability, thole, etc.), but not the identities of the particles they involve. It also cannot be used to add new particles or screenedPairs, only to change the parameters of existing ones.

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

• DrudeForce.h