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

From: Maurice de Koning <dekoning@...527...>
Date: Sat, 14 Apr 2018 13:43:21 -0300

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?