ActiveRotationalDiffusion

class hoomd.md.update.ActiveRotationalDiffusion(trigger, active_force, rotational_diffusion)

Bases: Updater

Updater to introduce rotational diffusion with an active force.

Parameters:

ActiveRotationalDiffusion works directly with hoomd.md.force.Active or hoomd.md.force.ActiveOnManifold to apply rotational diffusion to the particle quaternions \(\mathbf{q}_i\) in simulations with active forces. The persistence length of an active particle’s path is \(v_0 / D_r\).

In 2D, the diffusion follows \(\delta \theta / \delta t = \Gamma \sqrt{2 D_r / \delta t}\), where \(D_r\) is the rotational diffusion constant and the \(\Gamma\) unit-variance random variable.

In 3D, \(\hat{p}_i\) is a unit vector in 3D space, and the diffusion follows \(\delta \hat{p}_i / \delta t = \Gamma \sqrt{2 D_r / \delta t} (\hat{p}_i (\cos \theta - 1) + \hat{p}_r \sin \theta)\), where \(\hat{p}_r\) is an uncorrelated random unit vector.

When used with hoomd.md.force.ActiveOnManifold, rotational diffusion is performed in the tangent plane of the manifold.

Tip

Use hoomd.md.force.Active.create_diffusion_updater to construct a ActiveRotationalDiffusion instance.

Members inherited from AutotunedObject:

property kernel_parameters

Kernel parameters. Read more...

property is_tuning_complete

Check if kernel parameter tuning is complete. Read more...

tune_kernel_parameters()

Start tuning kernel parameters. Read more...

Members inherited from Integrator:

trigger

The trigger to activate this operation. Read more...

Members defined in ActiveRotationalDiffusion:

active_force

The active force associated with the updater. This is not settable after construction.

Type:

hoomd.md.force.Active

rotational_diffusion

The rotational diffusion as a function of time.

Type:

hoomd.variant.Variant