LIGGGHTS® - User Forum

I have been running simple shear stress simulations in LIGGGHTS using moving layers of particles along the top and bottom of the domain to mimic a Lees-Edwards boundary condition. I am able to get reasonable agreement with kinetic theory for normal and shear stresses for spherical particles using the compute stress/atom command. However, when I create spherical superquadric particles to run the same cases, I would expect very close to the same, exact result.

Dear LIGGGHTS users,

I want to relax the packing system statistically by minimizing the energy, and used the command "minimize 1.0e-4 1.0e-6 10000 100000".
The error message is "Minimization could not find thermo_pe compute". The manual explains this error as "This compute is created by the thermo command. It must have been explicitly deleted by a uncompute command". But I have not deleted this compute.

I am trying to run a simple simulation with a mesh file which is available in example as simple_chute.stl.
Now I am able to run simulation after changing the boundary to m m m but all of my particles are falling outside of domain.
Can anyone help me to fix this problem?

This is my script:

###############################################
# Example of LIGGGHTS #
# Flow only two particles in a plane surface #
###############################################

# Initialize

Hello,
I am trying to run a simulation where particles released freely from a height of 700 µm, due to gravitational and contact forces, these released powders freely deposited into the box and formed a powder bed. A roller is then applied to spread a 50 µm high layer of metal particles.
Can anyone share a code for that ? With which tutorials I can start or modify it or which command I should use ?
I am actually a total beginner. I would be glad if anyone can help through with the steps involved in the simulation.
thnx.

Hello,
I am trying to run a simulation where particles released freely from a height of 700 µm, due to gravitational and contact forces, these released powders freely deposited into the box and formed a powder bed. A roller is then applied to spread a 50 µm high layer of metal particles.
Can anyone share a code for that ? With which tutorials I can start or modify it or which command I should use ?
I am actually a total beginner. I would be glad if anyone can help through with the steps involved in the simulation.
thnx.

Hello Everyone!
I am working on the seepage-erosion problem, there is a cube with 0.01*0.01*0.01 simulation box with 6 mesh walls, and two group pariticles with different diameter, called fine and coarse, after consolidation with servo wall, I want to excude the top wall and the group fine particles, I tried to use three kind method which is discribed in documentation as followed:

Hello , LIGGGHTS user, I am trying to run a simulation where particle drop and flows one after another in some time interval.
I was able to make a flow of only one particle. When I tried to insert more than 1 particles with different insertion rates and insertevery, it doesn't drop particle in different time interval. In my case all particles are dropping at the same time.

Similarly, I use restart command too, but didn't work for me.

Here is my 'insert command'. I think I did mistake in these commands.

Dear LIGGGHTS users,

I used the contact model hertz, and set computeDissipatedEnergy as well as computeElasticPotential on. The manual says this setting saves the dissipated energy and elastic potential for use in fix calculate/dissipated_energy and fix calculate/normal_elastic_energy.

But when I output the variable f_calculate/dissipated_energy, it reports ERROR: Invalid fix ID in variable formula.

Could you please tell me how to solve this problem?

Thank you in advance.

Best wishes,
June

Dear LIGGGHTS users,

I want to monitor the change of total energy during dynamic relaxation. But I don't find the command to compute the total energy, and there is no thermodynamic output of the total energy. So how can I output the total energy of the system？

Thank you in advance.

Best wishes
June

Hello
I am a new user of LIGGGHTS-flexible fiber version. My problem is similar to the shear tutorial. Its different in a sense that in my case I intend to make cross-linked fiber bonds. In order to avoid 'bond loss error', I am using a kinetic energy (KE) based logic, i.e if KE of all atoms is less than a certain thresold, we form the cross-links, otherwise NOT.
Following is the logical statement I am using: