AmoebaAngleForce

class OpenMM::AmoebaAngleForce

This class implements an interaction between triplets of particles that varies with the angle between them. The interaction is defined by a 6th order polynomial. Only the quadratic term is set per-angle. The coefficients of the higher order terms each have a single value that is set globally.

To use it, create an AmoebaAngleForce object then call addAngle() once for each angle. After an angle has been added, you can modify its force field parameters by calling setAngleParameters(). This will have no effect on Contexts that already exist unless you call updateParametersInContext().

Methods

AmoebaAngleForce	Create an AmoebaAngleForce.
getNumAngles	Get the number of angle stretch terms in the potential function
setAmoebaGlobalAngleCubic	Set the global cubic term
getAmoebaGlobalAngleCubic	Get the global cubic term
setAmoebaGlobalAngleQuartic	Set the global quartic term
getAmoebaGlobalAngleQuartic	Get the global quartic term
setAmoebaGlobalAnglePentic	Set the global pentic term
getAmoebaGlobalAnglePentic	Get the global pentic term
setAmoebaGlobalAngleSextic	Set the global sextic term
getAmoebaGlobalAngleSextic	Get the global sextic term
addAngle	Add an angle term to the force field.
getAngleParameters	Get the force field parameters for an angle term.
setAngleParameters	Set the force field parameters for an angle term.
updateParametersInContext	Update the per-angle parameters in a Context to match those stored in this Force 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.

AmoebaAngleForce()

Create an AmoebaAngleForce().

int getNumAngles() const

Get the number of angle stretch terms in the potential function

void setAmoebaGlobalAngleCubic(double cubicK)

Set the global cubic term

Parameters

• cubicK – the cubic force constant for the angle

double getAmoebaGlobalAngleCubic() const

Get the global cubic term

Returns

global cubicK term

void setAmoebaGlobalAngleQuartic(double quarticK)

Set the global quartic term

Parameters

• quarticK – the quartic force constant for the angle

double getAmoebaGlobalAngleQuartic() const

Get the global quartic term

Returns

global quartic term

void setAmoebaGlobalAnglePentic(double penticK)

Set the global pentic term

Parameters

• penticK – the pentic force constant for the angle

double getAmoebaGlobalAnglePentic() const

Get the global pentic term

Returns

global penticK term

void setAmoebaGlobalAngleSextic(double sexticK)

Set the global sextic term

Parameters

• sexticK – the sextic force constant for the angle

double getAmoebaGlobalAngleSextic() const

Get the global sextic term

Returns

global sextic term

int addAngle(int particle1, int particle2, int particle3, double length, double quadraticK)

Add an angle term to the force field.

Parameters

• particle1 – the index of the first particle connected by the angle

• particle2 – the index of the second particle connected by the angle

• particle3 – the index of the third particle connected by the angle

• length – the equilibrium angle, measured in degrees

• quadraticK – the quadratic force constant for the angle, measured in kJ/mol/radian^2

Returns

the index of the angle that was added

void getAngleParameters(int index, int &particle1, int &particle2, int &particle3, double &length, double &quadraticK) const

Get the force field parameters for an angle term.

Parameters

• index – the index of the angle for which to get parameters

• particle1 – [out] the index of the first particle connected by the angle

• particle2 – [out] the index of the second particle connected by the angle

• particle3 – [out] the index of the third particle connected by the angle

• length – [out] the equilibrium angle, measured in degrees

• quadraticK – [out] the quadratic force constant for the angle, measured in kJ/mol/radian^2

void setAngleParameters(int index, int particle1, int particle2, int particle3, double length, double quadraticK)

Set the force field parameters for an angle term.

Parameters

• index – the index of the angle for which to set parameters

• particle1 – the index of the first particle connected by the angle

• particle2 – the index of the second particle connected by the angle

• particle3 – the index of the third particle connected by the angle

• length – the equilibrium angle, measured in degrees

• quadraticK – the quadratic force constant for the angle, measured in kJ/mol/radian^2

void updateParametersInContext(Context &context)

Update the per-angle 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 setAngleParameters() 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-angle parameters. The set of particles involved in an angle cannot be changed, nor can new angles 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