Displacement Vectors Display

[dx_yu]

Hello,

I am using OVITO Basic version 3.14.0 to visualize a shear system (flow direction along x, gradient along y).

Since LAMMPS may flip the simulation box when it is heavily deformed, I use the Unwrap modifier to obtain complete and continuous trajectories.

For easier visualization, I select a subset of particles using

ParticleIdentifier ==15||ParticleIdentifier ==33||ParticleIdentifier ==58||ParticleIdentifier ==42||ParticleIdentifier ==23||ParticleIden|ParticleIdentifier ==126||ParticleIdentifier ==128||ParticleIdentifier ==129||ParticleIdentifier ==175||ParticleIdentifier ==151||Partitifier ==9480||ParticleIdentifier ==9392||ParticleIdentifier ==9462||ParticleIdentifier ==63||ParticleIdentifier ==792||ParticleIdentifietifier ==228||ParticleIdentifier ==230||ParticleIdentifier ==237||ParticleIdentifier ==992||ParticleIdentifier ==279||ParticleIdentifierr ==771||ParticleIdentifier ==173||ParticleIdentifier ==64||ParticleIdentifier ==190||ParticleIdentifier ==93||ParticleIdentifier ==155||||ParticleIdentifier ==325||ParticleIdentifier ==310||ParticleIdentifier ==336||ParticleIdentifier ==309||ParticleIdentifier ==342||PartParticleIdentifier ==126||ParticleIdentifier ==128||ParticleIdentifier ==129||ParticleIdentifier ==175||ParticleIdentifier ==151||Particldentifier ==411||ParticleIdentifier ==9797||ParticleIdentifier ==420||ParticleIdentifier ==425||ParticleIdentifier ==536||ParticleIdentieIdentifier ==156||ParticleIdentifier ==282||ParticleIdentifier ==255||ParticleIdentifier ==277||ParticleIdentifier ==932||ParticleIdenti=378||ParticleIdentifier ==482||ParticleIdentifier ==9871||ParticleIdentifier ==514||ParticleIdentifier ==497||ParticleIdentifier ==533|fier ==228||ParticleIdentifier ==230||ParticleIdentifier ==237||ParticleIdentifier ==992||ParticleIdentifier ==279||ParticleIdentifier ==leIdentifier ==617||ParticleIdentifier ==615||ParticleIdentifier ==578||ParticleIdentifier ==620||ParticleIdentifier ==1332||ParticleIde168||ParticleIdentifier ==263||ParticleIdentifier ==235||ParticleIdentifier ==316||ParticleIdentifier ==9786||ParticleIdentifier ==323||P ==727||ParticleIdentifier ==720||ParticleIdentifier ==7||ParticleIdentifier ==680||ParticleIdentifier ==663||ParticleIdentifier ==664||articleIdentifier ==325||ParticleIdentifier ==310||ParticleIdentifier ==336||ParticleIdentifier ==309||ParticleIdentifier ==342||ParticlecleIdentifier ==768Identifier ==9722||ParticleIdentifier ==9680||ParticleIdentifier ==368||ParticleIdentifier ==379||ParticleIdentifier ==398||ParticleIdentifier ==411||ParticleIdentifier ==9797||ParticleIdentifier ==420||ParticleIdentifier ==425||ParticleIdentifier ==536||ParticleIdentifier 
==435||ParticleIdentifier ==438||ParticleIdentifier ==476||ParticleIdentifier ==9790||ParticleIdentifier ==386||ParticleIdentifier ==378||ParticleIdentifier ==482||ParticleIdentifier ==9871||ParticleIdentifier ==514||ParticleIdentifier ==497||ParticleIdentifier ==533||ParticleIdentifier ==535||ParticleIdentifier ==541||ParticleIdentifier ==542||ParticleIdentifier ==545||ParticleIdentifier ==585||ParticleIdentifier ==617||ParticleIdentifier ==615||ParticleIdentifier ==578||ParticleIdentifier ==620||ParticleIdentifier ==1332||ParticleIdentifier ==594||ParticleIdentifier ==633||ParticleIdentifier ==659||ParticleIdentifier ==596||ParticleIdentifier ==691||ParticleIdentifier ==727||ParticleIdentifier ==720||ParticleIdentifier ==7||ParticleIdentifier ==680||ParticleIdentifier ==663||ParticleIdentifier ==664||ParticleIdentifier ==10080||ParticleIdentifier ==679||ParticleIdentifier ==704||ParticleIdentifier ==767||ParticleIdentifier ==766||ParticleIdentifier ==768

I observed that the trajectories generated by the Generate Trajectory modifier look correct and
as expected—particles at larger y positions move more.

However, the displacement vectors shown by the Displacement modifier seem confusing.

I am not sure if this is normal or expected behavior for the Displacement modifier in OVITO.
I just wanted to bring up this topic as a reminder

Thank you.

[stukowski]

To better help you, I think it would be useful to share the full trajectory file(s) with us. Either here in this forum - or by sending them to [email protected]. Thanks.

What are your affine mapping settings for the Displacement Vectors modifier? Since you have unwrapped the particle trajectories, you should probably turn off the “use minimum image convention” option. This option can mess up the displacement vectors when the deformation of the cell is very large like in this case.

[dx_yu]

I apologize for not showing the settings of the Displacement modifier earlier. After turning off the “Use minimum image convention” option, the displacement vectors are as follows:

They look more normal now.

I have also sent you my 2D dump file (the file is quite large, so I cannot share it here directly).

[stukowski]

Thanks for sending the trajectory file.

After importing your file, I’ve also used the Unwrap Trajectories and Displacement Vectors modifiers and got the following picture, which is more in line with my expectations:

I am wondering why your displacement vectors are longer and extend further to the left. The only explanation I can think of is that you have set a scaling factor greater than 1 for the displacement vector visualization. Could please double check your vector display settings?

[dx_yu]

Yes, you are right. After setting the scaling factor to 1, I obtained the figure you showed.
Thank you for your help.