AmoebaBondForce¶
-
class
OpenMM
::
AmoebaBondForce
¶ This class implements an interaction between pairs of particles that varies with the distance between them. The interaction is defined by a 4th order polynomial. Only the quadratic term is set per-bond. The coefficients of the higher order terms each have a single value that is set globally.
To use it, create an
AmoebaBondForce
object then calladdBond()
once for each bond. After a bond has been added, you can modify its force field parameters by callingsetBondParameters()
. This will have no effect on Contexts that already exist unless you callupdateParametersInContext()
.Methods
Create an
AmoebaBondForce
.Get the number of bond stretch terms in the potential function
Set the global cubic term
Get the global cubic term
Set the global quartic term
Get the global quartic term
Add a bond term to the force field.
Get the force field parameters for a bond term.
Set the force field parameters for a bond term.
Update the per-bond parameters in a
Context
to match those stored in thisForce
object.Set whether this force should apply periodic boundary conditions when calculating displacements.
Returns whether or not this force makes use of periodic boundary conditions.
-
AmoebaBondForce
()¶ Create an
AmoebaBondForce()
.
-
int
getNumBonds
() const¶ Get the number of bond stretch terms in the potential function
-
void
setAmoebaGlobalBondCubic
(double cubicK)¶ Set the global cubic term
- Parameters
cubicK – the cubic force constant for the bond
-
double
getAmoebaGlobalBondCubic
() const¶ Get the global cubic term
- Returns
global cubicK term
-
void
setAmoebaGlobalBondQuartic
(double quarticK)¶ Set the global quartic term
- Parameters
quarticK – the quartic force constant for the bond
-
double
getAmoebaGlobalBondQuartic
() const¶ Get the global quartic term
- Returns
global quartic term
-
int
addBond
(int particle1, int particle2, double length, double quadraticK)¶ Add a bond term to the force field.
- Parameters
particle1 – the index of the first particle connected by the bond
particle2 – the index of the second particle connected by the bond
length – the equilibrium length of the bond, measured in nm
quadraticK – the quadratic force constant for the bond
- Returns
the index of the bond that was added
-
void
getBondParameters
(int index, int &particle1, int &particle2, double &length, double &quadraticK) const¶ Get the force field parameters for a bond term.
- Parameters
index – the index of the bond for which to get parameters
particle1 – [out] the index of the first particle connected by the bond
particle2 – [out] the index of the second particle connected by the bond
length – [out] the equilibrium length of the bond, measured in nm
quadraticK – [out] the quadratic force constant for the bond
-
void
setBondParameters
(int index, int particle1, int particle2, double length, double quadraticK)¶ Set the force field parameters for a bond term.
- Parameters
index – the index of the bond for which to set parameters
particle1 – the index of the first particle connected by the bond
particle2 – the index of the second particle connected by the bond
length – the equilibrium length of the bond, measured in nm
quadraticK – the quadratic force constant for the bond
-
void
updateParametersInContext
(Context &context)¶ Update the per-bond parameters in a
Context
to match those stored in thisForce
object. This method provides an efficient method to update certain parameters in an existingContext
without needing to reinitialize it. Simply callsetBondParameters()
to modify this object’s parameters, then callupdateParametersInContext()
to copy them over to theContext
.The only information this method updates is the values of per-bond parameters. The set of particles involved in a bond cannot be changed, nor can new bonds be added.
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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
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