Author Topic: Ellipsoidal orientations problem  (Read 153 times)

ltse

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Ellipsoidal orientations problem
« on: April 16, 2018, 02:50:57 PM »
Hi,

I have a problem to see any change in the orientations of ellipsoidal particles regardless of any change in quartenion in the input file. For example, lets say this is the input file:

ITEM: TIMESTEP
0
ITEM: NUMBER OF ATOMS
2
ITEM: BOX BOUNDS pp pp pp
0 100
0 100
0 100
ITEM: ATOMS id type x y z qw qi qj qw s1 s2 s3
1 1 25 25 25 0.707 0.5 0 0.5 25 25 5
2 1 75 75 75 0.5 -0.6124 0.6124 0 25 25 5

In my ovito, after adjusting parameters manually, I only see two ellipsoids with no rotations at all. Same happens if I change angle and vector of quaternions. I am not sure what I am doing wrong here. I appreciate any comments.

Regards,
Robin

Alexander Stukowski

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Re: Ellipsoidal orientations problem
« Reply #1 on: April 16, 2018, 04:21:41 PM »
Hi Robin,

I can only speculate, but here is what I think is the problem:

OVITO doesn't know that the four columns named "qw", "qi", etc. in your file contain the orientation information. The reason is that LAMMPS doesn't seem to have a standard naming convention for these auxiliary properties. Thus, you need to tell the OVITO explicitly how to interpret these file columns. For OVITO to use the orientation information rotate the ellipsoids, the quaternion values from the file need to be mapped to OVITO's "Orientation" particle property. This is explained in the last paragraph on this page of the manual:

http://ovito.org/manual/howto.aspherical_particles.html

If you don't know where to find the "Edit column mapping" button, see the screenshot here:

http://ovito.org/manual/usage.import.html

-Alex