Help with rotational Brownian Dynamics

[luis roberto carlos ochoa]

Hi Hoomd users!!

I hope you could help me with this. I want to study the brownian dynamics BD of a rigid body using Hoomd. According to the documentation that I found, the BD method works like this:

However, I'd like to apply on my system also the rotational part of the BD. So probably the set of equations to describe what I want would be:

But I'm not sure if Hoomd by default considers the rotational form of BD or I have to sort of create it, because whenever I try to group all the molecules in the rigid bodies and I pass them to BD method I get the next warning:

"BD does not operate on constituent particles" . 

That makes me think, BD in Hoomd just takes into account the traslational part of BD equations.

Please, give me all your suggestions. This is very important for me :) 

[Joshua Anderson]

Luis,

Yes, the BD integrator in HOOMD will integrate the rotational degrees of freedom. This is not mentioned in the documentation, but should be.

https://github.com/glotzerlab/hoomd-blue/blob/f8c1c45b78898aec01f36d45c93701ba817b6a21/hoomd/md/TwoStepBD.cc#L135-L199

When you pass a group or filter to an integration method, only provide it with the central particles to the rigid bodies. The integration methods in HOOMD operate only on the degrees of freedom of these particles.

------
Joshua A. Anderson, Ph.D.
Research Area Specialist, Chemical Engineering, University of Michigan

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[luis roberto carlos ochoa]

Thank u very much!! It really helped