Coupling of Orientations and Bond direction

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kmo...@ucsb.edu

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Aug 2, 2021, 6:39:40 PMAug 2
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Hi all,

I am interested in studying worm-like chain polymers using Brownian dynamics simulations. One thing I'd like to include is an active force on the "head" of the polymer chain.

I'd like to know if there is a way to couple the orientation of the head group with the contour of the chain

 --> In essence, I'd like to define the orientation direction by the vector r_N  -  r_(N-1).
Where r_N is the last bead position, and r_(N-1) is the second to last bead position.

This way, the head orientation vector does not move because the head is rotating in place; instead it rotates because the rest of the polymer around it has moved.

A workaround that I can imagine would be to implement a rigid body constraint between the last two monomers, but I don't believe it is possible to bond a rigid body through harmonic bonds and angles to the rest of the chain, is that correct?


Thank you for your help!
Kevin Modica

Joshua Anderson

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Aug 3, 2021, 7:53:34 AMAug 3
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Kevin,

Yes, you could write an Updater that sets particle orientations.

Yes, you can connect bonds and angles to rigid body constituent particles.
------
Joshua A. Anderson, Ph.D.
Research Area Specialist, Chemical Engineering, University of Michigan
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