# RBTorsionForce Class Reference

This class implements an interaction between groups of four particles that varies with the torsion angle between them according to the Ryckaert-Bellemans potential. More...

Inheritance diagram for RBTorsionForce:

List of all members.

## Public Member Functions

def | getNumTorsions
| getNumTorsions(self) -> int
def | addTorsion
| addTorsion(self, int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5) -> int
def | getTorsionParameters
| getTorsionParameters(self, int index)
def | setTorsionParameters
| setTorsionParameters(self, int index, int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5)
def | updateParametersInContext
| updateParametersInContext(self, Context context)
def | __init__
| __init__(self) -> RBTorsionForce __init__(self, RBTorsionForce other) -> RBTorsionForce
def | __del__
| __del__(self)

## Public Attributes

| this

## Detailed Description

This class implements an interaction between groups of four particles that varies with the torsion angle between them according to the Ryckaert-Bellemans potential.

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

## Member Function Documentation

def __del__ | ( |  | self | ) |

__del__(self)

Reimplemented from Force.

def __init__ | ( |  | self,
|  |  | args |
| ) |  |  |

__init__(self) -> RBTorsionForce __init__(self, RBTorsionForce other) -> RBTorsionForce

Create a RBTorsionForce.

def addTorsion | ( |  | self,
|  |  | args |
| ) |  |  |

addTorsion(self, int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5) -> int

Add a Ryckaert-Bellemans torsion term to the force field.

Parameters:

  | particle1 | the index of the first particle forming the torsion
  | particle2 | the index of the second particle forming the torsion
  | particle3 | the index of the third particle forming the torsion
  | particle4 | the index of the fourth particle forming the torsion
  | c0 | the coefficient of the constant term, measured in kJ/mol
  | c1 | the coefficient of the 1st order term, measured in kJ/mol
  | c2 | the coefficient of the 2nd order term, measured in kJ/mol
  | c3 | the coefficient of the 3rd order term, measured in kJ/mol
  | c4 | the coefficient of the 4th order term, measured in kJ/mol
  | c5 | the coefficient of the 5th order term, measured in kJ/mol

def getNumTorsions | ( |  | self | ) |

getNumTorsions(self) -> int

Get the number of Ryckaert-Bellemans torsion terms in the potential function

def getTorsionParameters | ( |  | self,
|  |  | args |
| ) |  |  |

getTorsionParameters(self, int index)

Get the force field parameters for a Ryckaert-Bellemans torsion term.

Parameters:

  | index | the index of the torsion for which to get parameters
  | particle1 | the index of the first particle forming the torsion
  | particle2 | the index of the second particle forming the torsion
  | particle3 | the index of the third particle forming the torsion
  | particle4 | the index of the fourth particle forming the torsion
  | c0 | the coefficient of the constant term, measured in kJ/mol
  | c1 | the coefficient of the 1st order term, measured in kJ/mol
  | c2 | the coefficient of the 2nd order term, measured in kJ/mol
  | c3 | the coefficient of the 3rd order term, measured in kJ/mol
  | c4 | the coefficient of the 4th order term, measured in kJ/mol
  | c5 | the coefficient of the 5th order term, measured in kJ/mol

def setTorsionParameters | ( |  | self,
|  |  | args |
| ) |  |  |

setTorsionParameters(self, int index, int particle1, int particle2, int particle3, int particle4, double c0, double c1, double c2, double c3, double c4, double c5)

Set the force field parameters for a Ryckaert-Bellemans torsion term.

Parameters:

  | index | the index of the torsion for which to set parameters
  | particle1 | the index of the first particle forming the torsion
  | particle2 | the index of the second particle forming the torsion
  | particle3 | the index of the third particle forming the torsion
  | particle4 | the index of the fourth particle forming the torsion
  | c0 | the coefficient of the constant term, measured in kJ/mol
  | c1 | the coefficient of the 1st order term, measured in kJ/mol
  | c2 | the coefficient of the 2nd order term, measured in kJ/mol
  | c3 | the coefficient of the 3rd order term, measured in kJ/mol
  | c4 | the coefficient of the 4th order term, measured in kJ/mol
  | c5 | the coefficient of the 5th order term, measured in kJ/mol

def updateParametersInContext | ( |  | self,
|  |  | args |
| ) |  |  |

updateParametersInContext(self, Context context)

Update the per-torsion 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 setTorsionParameters() to modify this object's parameters, then call updateParametersInState() to copy them over to the Context.

The only information this method updates is the values of per-torsion parameters. The set of particles involved in a torsion cannot be changed, nor can new torsions be added.

## Member Data Documentation

this

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

- openmm.py