I encounter difficulties in running a 2D simulation. A rigid rod consisting of 200 atoms is attached to a spring. The rod should only move in the xy-plane. Therefor I put 'dimension 2d' in the input file, then setup a simulation box with a small z-dimension with periodic BCs in z and fix enforce 2d. The atoms are treated as a rigid rod via the fix rigid command with force components in x and y direction and torque around the x-axis. NVE integration should be done with fix rigid.
Although I apply a strong spring force, the rod doesn't move at all?
I attach an input file to demonstrate this behaviour.
I ran this input file with LIGGGHTS 1.2.5 beta compiled at 2011-02-15.
Maybe someone could help me to sort out the mistakes that are probably buried in my input file or to bash bugs in LIGGHTS.
Best regards,
Thomas Wagner.
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 in.2D.txt | 1.28 KB |
ckloss | Tue, 02/15/2011 - 16:51
There is nothing
There is nothing attached...
Cheers,
Christoph
ckloss | Wed, 02/16/2011 - 11:02
After a short glance, I guess
After a short glance, I guess the timestep is pretty high - you are using SI units, and also the spring point may be too far away. I would advise you to start with a simple example (eg with fix nve/sphere instead of fix rigid), and add commands/complexity step by step to see which one is causing troubles
Christoph
marketos | Tue, 02/22/2011 - 11:55
Hi Thomas, This is not so
Hi Thomas,
This is not so relevant to your question but just in case.. (hopefully all will be fine)
It will be worth checking whether LIGGGHTS uses the correct moment of inertia and volume of particles in 2D, just in case it uses the 3D formulae. Also in some of the pairs where contact area is required there might be pi*Radius^2 used instead of 2*radius which seems more logical for 2D.
Cheers,
George