LIGGGHTS® - User Forum

LIGGGHTS® related topics can be discussed here: discussion about models, installation, feature requests and general discussion

use the the variable command to flag specific atoms to exclude from a group

Submitted by zpy2021 on Tue, 01/19/2021 - 08:04

Dear LIGGGHTS users!
I want to use the variable command to include and exclude the specific particles from a group, and I used the similar commands like that in the Docs as following:

compute 1 all pe/atom
compute 2 all reduce sum c_1
thermo_style custom step temp pe c_2
run 0
variable eatom atom "c_1 > -3.0"
group hienergy variable eatom

errors with neighbor multi

Submitted by June on Mon, 01/18/2021 - 07:13

Dear LIGGGHTS users,

I am simulating packing systems with a very wide range of particle size, and use "neighbor 0.002 multi"+"communicate multi vel yes". However, the output kinetic energy and pressure are both zero. When using "neighbor 0.002 bin"+"communicate single vel yes", the output kinetic energy and pressure are not zero.

Could you please tell me the reason?
Any help will really be appreciated.

Best wishes
June

Stress/atom for superquadric particles

Submitted by RonMexico on Fri, 01/08/2021 - 18:04

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.

Energy minimization

Submitted by June on Fri, 01/08/2021 - 10:19

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.

Particles are falling outside of domain.

Submitted by laudari on Fri, 01/08/2021 - 08:06

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

how to release powder from a height

Submitted by nada on Thu, 01/07/2021 - 14:37

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.

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