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

• 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

• 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

• 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

• 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.

• 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
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.

• 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
void setAngleParameters(int index, int particle1, int particle2, int particle3, 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
• length – the equilibrium angle, measured in degrees
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