LIGGGHTS® - User Forum

Hi, All:

I currently have a problem that needs to consider a type of particle that is composed of two bonded spheres (one with positive electric charge and one with negative charge), so basically I am trying to first bond particles together and then assign electric charges to them. (See attached figure)

I am wondering if there is any existing examples using LIGGGHTS that can:
1. simulate the electro-static forces between particles?
2. bond the particles together

Thanks for any suggestions in advance!

Roy

Hi,

In trying to calculate the number of contacts per particle, I found that contact/atom gives me the incorrect result. I have attached a simple test: 2 particles (particles #7 and #8) sandwiched between two layers of 3 particles. From coord/atom and from the contact force dump, each particle clearly has 4 contacting neighbors, yet contact/atom does not give this result (it gives 3). Any ideas?

Hello,

I did a simulation using force controlled doundaries. when i try to unfix it, then i got the erro message as follows:

ERROR: Fix mesh/surface/stress/servo (id zcover_1): illegal unfix command, may not unfix a mesh while a fix move is applied.Unfix the fix move/mesh first (fix_mesh.cpp:242)

but the problem is that i did not use fix move/mesh, why am i not allowed to unfix the "fix mesh/surface/stress/servo"?

Is there a way to restart a simulation that has fix move/mesh with the "wiggle" style, and have the simulation continue the oscillatory motion from where it left off? According to the docs (and some tests that I ran), the wiggle style uses X0 and delta from "the time the fix is specified" in the input file. In a restarted simulation, this time is *not* the same as in the original simulation that produced the restart file. I want the fix move/mesh motion to continue as if from t = 0, not t = whatever in the restart file.

Has someone managed to automatically calculate the "Estimated Time of Arrival" of the calculation?

In my continuing work on thermal expansion for pebble beds, I've begun looking at the evolution of the average force magnitude on each pebble.

Hi everyone,
I met an error as the "Invalid bond style" when it read the restart file. I am using the atom style of granular that it could not be used with the bond style. Does anyone know how to modify it or any thing that could be caused to this? Thanks.

I've been trying to debug some nuclear heating and thermal expansion adaptions that I've been having with my input script. To help with the debugging I just took the input script from heatTransfer_1 example and added a few lines of code. When I run this on my laptop (LIGGGHTS 2.3 on a Mac) there's no problem.

If I take this exact same code and run it on my lab's server computer (LIGGGHTS 2.3 on Ubuntu) it goes all wonky. The pebbles act as if there are no walls, and the particles just fly out of the system. I narrowed it down to a single line of code. The suspect line is:

For LIGGGHTS, I just noticed the periodic boundary condition is enforced during the post-processing by lpp. Is there a way to do it in liggghts so the particles exiting the region will come back through the boundary in the other end? Really appreciate!

Hi Christoph,

Thank you very much for your reply, Sir i found that once i generate restart file for my cylindrical couette flow simulation after 10000000 timesteps ,

i ran this restart code ,

#------------------------------------------------------------

atom_style sphere
newton off
communicate single vel yes
atom_modify map array

#-------------------------------------------------------------

timestep 0.0000002
read_restart data.10000000

#-------------------------------------------------------------