LIGGGHTS® - User Forum

Hi,
I want to change the value of a variable after a certain number of timesteps. I tried to do this using the following lines in my script

run 10 pre no post no every 1 &
"variable vke equal step" &
"if ${vke} > 5 then 'variable xp0 equal 1' "

I get an error after the 6th timestep (when the if condition becomes true): ERROR: Unknown command: 'variable

So it seems the nested quotes are a problem. I have also tried changing the quotes to

"if '${vke} > 5' then 'variable xp0 equal 1' "

but in this case the if condition is just completely ignored.

Hi,

Does anybody know if the LIGGGHTS programme can be used in two dimensional conditions? In the source code, somewhere I see it says it is only valid in 3D. How can I do with LIGGGHTS to carry out a 2D biaxial test?

Thanks.

Jerry

ave/spatial problem for obtaining a section averaging

Hallo everyone ,,
im running a simulation on LAMMPS and i need to have a section with averaging values of particles to compare it with other results ,,,so i need to creat a box in the middle of the box and then average the values of the particles within this BOX ,, the problem is that i cant define 3d bin !! i always get error message when i define more than one dimension in fix command !!

dimension 3
boundary p fs p

Hi,
Is it possible to dump snapshots in a format which can be read by EnSight? Or, is there a way to convert them into ensight format by pizza?
Any clue will be appreciated.
Thanks
Ram

Hi, all

Is it possible (or simply naive) to run the MD and DEM simultaneously in one model? I am wondering if it is feasible to use a cluster of atoms to assemble a nano granular particle which can contact with other particles? The interaction between the atoms within one particle is governed by MD potential function (e.g. Lennard Jones) while the contact between particles follows the contact law (e.g. Hertz).

Any suggestion and discussion is appreciated.

cheers

Yang

Hi!
Has anybody got LIGGGHTS working under Sun Grid Engine with $round_robin -scheme? I've only managed to get it work with $fill_up and even then every calculating node for the simulation has been on the same computer. I'm using OpenMPI-1.5.3 and it has been compiled --with-sge (haven't seen any difference, if this flag has been used or not...). Without SGE it works perfectly fine. Some simple hostname calling scripts under SGE with mpirun works also fine.

- Timo

Hi, all

How to choose an appropriate timestep in LIGGGHTS? In the examples, I presume the timestep, e.g. 0.00001, is not generally applicable.

Normally a ratio of the out-of-balance force over the average contact force is used to assess if the granular system is stable or not. I'm just wondering whether this is robust in LIGGGHTS or I have to take care of the timestep by myself in each simulation?

cheers

Hi all,

I have been scratching my head over this one today - my simulation works fine unless I try to dump the per-particle forces with compute pair/gran/local - then it runs for a while, but crashes with:

2374000 1123 6.1525987
[comp-l06:09946] *** Process received signal ***
[comp-l06:09946] Signal: Segmentation fault (11)
[comp-l06:09946] Signal code: Address not mapped (1)
[comp-l06:09946] Failing at address: (nil)
[comp-l06:09946] [ 0] /lib/libpthread.so.0(+0xf8f0) [0x7f19103438f0]

Hi all,

I minor but potentially useful feature request here - would it be possible to add a simple binary flag to the compute pair/gran/local that shows if an interaction is periodic? For contact force chain and similar visualisation this would make it easier to avoid connecting points at opposite sides of a simulation domain etc.

Regards, Mark

Hi Christoph,
I found that LIGGGHTS can not dump stresses on the CAD cylindrical wall properly when the ratio of the diameter of beads to the diameter of cylinder is bigger than 0.02; however, below this ratio, the stress profile is good. But, using this low ratio is computationally expensive. Is there another way to do so?

Thanks,
Ram