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Re: [lammps-users] Angular velocities in principal axes frame
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Re: [lammps-users] Angular velocities in principal axes frame

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 16 Apr 2018 14:11:53 -0400

On Sat, Apr 14, 2018 at 12:43 PM, Maurice de Koning
<dekoning@...527...> wrote:
> I’m interested in computing so-called rotational diffusion constants for rigid water molecules (say TIP4P, using shake to maintain the constraints).
> One of the definitions for the rotational mean-squared displacement requires access to
> molecular angular velocities expressed in the instantaneous principal axes frame. Searching
> in the manual it seems that such angular velocities are available only with respect to the simulation
> box frame directions. On the other hand, I’ve seen that for certain calculations (body particles), lammps
> does compute the principal axes internally.
> Would you have any suggestions as to how to compute angular velocities in the principal axes frame?

please have a look at compute angmom/chunk. i would expect it to be
straightforward to modify it to compute and output the angular
velocities you are looking for instead of the angular momentum.
or you could think about recovering it in post-processing by using
both, compute angmom/chunk and inertia/chunk.


> Thanks!
> Maurice
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Dr. Axel Kohlmeyer  akohlmey@...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.