# AmoebaInPlaneAngleForce¶

class OpenMM::AmoebaInPlaneAngleForce

This class implements an interaction at trigonal centers corresponding to the projected in-plane angle bend energy between four particles. The interaction is defined by a 6th order polynomial in the angle between them. 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 AmoebaInPlaneAngleForce 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

 AmoebaInPlaneAngleForce Create an AmoebaAngleForce. getNumAngles Get the number of in-plane angle terms in the potential function setAmoebaGlobalInPlaneAngleCubic Set the global cubic term getAmoebaGlobalInPlaneAngleCubic Get the global cubic term setAmoebaGlobalInPlaneAngleQuartic Set the global quartic term getAmoebaGlobalInPlaneAngleQuartic Get the global quartic term setAmoebaGlobalInPlaneAnglePentic Set the global pentic term getAmoebaGlobalInPlaneAnglePentic Get the global pentic term setAmoebaGlobalInPlaneAngleSextic Set the global sextic term getAmoebaGlobalInPlaneAngleSextic 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.
AmoebaInPlaneAngleForce()

Create an AmoebaAngleForce.

int getNumAngles() const

Get the number of in-plane angle terms in the potential function

void setAmoebaGlobalInPlaneAngleCubic(double cubicK)

Set the global cubic term

• cubicK – the cubic force constant for the angle
double getAmoebaGlobalInPlaneAngleCubic() const

Get the global cubic term

Returns: global cubicK term
void setAmoebaGlobalInPlaneAngleQuartic(double quarticK)

Set the global quartic term

• quarticK – the quartic force constant for the angle
double getAmoebaGlobalInPlaneAngleQuartic() const

Get the global quartic term

Returns: global quartic term
void setAmoebaGlobalInPlaneAnglePentic(double penticK)

Set the global pentic term

• penticK – the pentic force constant for the angle
double getAmoebaGlobalInPlaneAnglePentic() const

Get the global pentic term

Returns: global penticK term
void setAmoebaGlobalInPlaneAngleSextic(double sexticK)

Set the global sextic term

• sexticK – the sextic force constant for the angle
double getAmoebaGlobalInPlaneAngleSextic() const

Get the global sextic term

Returns: global sextic term
int addAngle(int particle1, int particle2, int particle3, int particle4, double length, double quadraticK)

Add an angle term to the force field.

• 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
• particle4 – the index of the fourth particle connected by the angle
• length – the equilibrium angle, measured in radians
Returns: the index of the angle that was added
void getAngleParameters(int index, int &particle1, int &particle2, int &particle3, int &particle4, double &length, double &quadraticK) const

Get the force field parameters for an angle term.

• 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
• particle4 – [out] the index of the fourth particle connected by the angle
• length – [out] the equilibrium angle, measured in radians
void setAngleParameters(int index, int particle1, int particle2, int particle3, int particle4, double length, double quadraticK)

Set the force field parameters for an angle term.

• 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
• particle4 – the index of the fourth particle connected by the angle
• length – the equilibrium angle, measured in radians
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