md.angle¶
Overview
Constructs the angular bond potential. 

Harmonic angle potential. 

Cosine squared angle potential. 
Details
Angle potentials.

class
hoomd.md.angle.
Angle
¶ Bases:
hoomd.md.force.Force
Constructs the angular bond potential.
Note
Angle
is the base class for all angular potentials. Users should not instantiate this class directly.

class
hoomd.md.angle.
Cosinesq
¶ Bases:
hoomd.md.angle.Angle
Cosine squared angle potential.
The command angle.cosinesq specifies a cosine squared potential energy between every triplet of particles with an angle specified between them.
\[V(\theta) = \frac{1}{2} k \left( \cos\theta  \cos\theta_0 \right)^2\]where \(\theta\) is the angle between the triplet of particles. This angle style is also known as g96, since they were used in the gromos96 force field. These are also the types of angles used with the coarsegrained MARTINI force field.

params
¶ The parameter of the harmonic bonds for each particle type. The dictionary has the following keys:
k
(float
, required)  potential constant (in units of energy/radians^2)t0
(float
, required)  rest angle \(\theta_0\) (in units radians)
 Type
TypeParameter[
angle type
, dict]
Parameters \(k\) and \(\theta_0\) must be set for each type of angle in the simulation. Note that the value of \(k\) for this angle potential is not comparable to the value of \(k\) for harmonic angles, as they have different units.
Examples:
cosinesq = angle.Cosinesq() cosinesq.params['polymer'] = dict(k=3.0, t0=0.7851) cosinesq.params['backbone'] = dict(k=100.0, t0=1.0)


class
hoomd.md.angle.
Harmonic
¶ Bases:
hoomd.md.angle.Angle
Harmonic angle potential.
The command angle.harmonic specifies a harmonic potential energy between every triplet of particles with an angle specified between them.
\[V(\theta) = \frac{1}{2} k \left( \theta  \theta_0 \right)^2\]where \(\theta\) is the angle between the triplet of particles.

params
¶ The parameter of the harmonic bonds for each particle type. The dictionary has the following keys:
k
(float
, required)  potential constant (in units of energy/radians^2)t0
(float
, required)  rest angle (in units radians)
 Type
TypeParameter[
angle type
, dict]
Examples:
harmonic = angle.Harmonic() harmonic.params['polymer'] = dict(k=3.0, t0=0.7851) harmonic.params['backbone'] = dict(k=100.0, t0=1.0)
