variable parameters in DPD pair potential

[Deepak Mangal]

Hi all,

I want to use variable gamma (based on distance between particles) in DPD pair potential by including short-range lubrication interactions between particles. Can I do that using custom action?

Thanks,

Deepak Mangal

[Brandon Butler]

Hey Deepak,

Yes, you can. You can also just run a set number of steps in a while or for loop before changing the potential again. To use a custom action see the tutorial in the official documentation, and create a class definition that allows for the class to take a DPD potential object and update its attributes in its act method.

Best,

Brandon

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Brandon Butler
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PhD Candidate, Chemical Engineering and Scientific Computing | Glotzer Lab, University of Michigan
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[Deepak Mangal]

Hi Brandon,

Thank you for your quick reply. I actually was not asking about updating DPD pair attributes with timestep. The DPD pair attributes are specific to particle types, but with lubrication interaction it will depend on the distance between a pair of particles also. So, I wanted to know how I can implement it using custom action.

Thanks,

Deepak

[Joshua Anderson]

Deepak,

The functional form of the DPD potential is written in C++ and compiled into the shared object file. You cannot modify it using Python using a custom action.

See: https://github.com/glotzerlab/hoomd-blue/blob/7b450cc7eb65e49e4fa8ac7be490103d42c22326/hoomd/md/EvaluatorPairDPDThermo.h#L268-L283
------
Joshua A. Anderson, Ph.D.
Research Area Specialist, Chemical Engineering, University of Michigan

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[Deepak Mangal]

Hi Dr. Anderson,

Thank you for your reply. To use variable parameters in DPD pair potential, I created a new pair potential class (attached here), and installed the HOOMD-Blue package with the new class. The package is installed successfully, but hoomd.md.pair module doesn't recognize the new pair potential. Could you please suggest what changes I should make in the HOOMD-Blue package to include new pair potential class?

Sincerely,

Deepak Mangal

[Joshua Anderson]

Deepack,

I have an open pull request that adds documentation on this topic to ARCHITECTURE.md. You can find an overview there: https://github.com/glotzerlab/hoomd-blue/pull/1230

You can also search recent pull requests for an example of one adding a new potential.

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

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> <EvaluatorPairDPDMorseThermo.h>