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.
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.

bool usesPeriodicBoundaryConditions() const

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

Returns:true if nonbondedMethod uses PBC and false otherwise