LIGGGHTS® - User Forum

Hi all,

The manual describes about volume_limit of fix/particletemplate/sphere that LIGGGHTS will throw an error if the particle volume too small compared to machine precision. My question is how to adjust machine precision with default limit 1e-12 of LIGGGHTS. For examples, I'm playing with particle's size D=50micron that has volume of 5.4e-14 m3. It's obviously lower than default value. Does it cause serious error to simulation result?

Dear All,

In my simulation ,I am trying to print out all data from the command .. wall/gran/local .. to be in one txt file but I could not.

In Pre-atom or global data, It can be defined in (variable equal command) and then use (fix print command) to store all the data.

I am looking to print (local data) in one txt file (like print do). Is there any way to do that?

thank you in advance for your help.

Regards.
Chris

Hi all,

I am trying to calculate the total number of contacts.
In my simulation, I used( compute contact/atom command) to calculate the number of contacts. Then, I used (fix print command )to store all the data in order to sum all the numbers and get the total number of contacts.

variable C1 equal c_NOC
fix cont all print 10 "${C1}" file contact.txt screen no
compute NOC gr contact/atom

Hi All,
I am a new user.
I implemented the following simulation [in.packing]:
Box with periodic boundaries filled with 9261 particles with size and velocities read from data file I created [data.packing].
I am using a linear spring dashpot contact model. Quantities are scaled in such a way that are dimensionless: M=10-9 kg, L=10-3m, T=10-6s.

I acquire the dump files in Matlab and, for each particle, I compute the overlaps with other particles and the elastic forces (output from LIGGGHTS) acting on it.

Hi everyone,

Hello, I've done a few simulations trying with 1, 4 and 8 processors, and I got higher calculation time for 4, and even more, for 8 processors. In the input script, I tried two thing. First I didn't set any parameter for "Processors", and then I try with several combinations. I noticed that I could get better calculation time chosing aproppiate values in "Processors", but it is not better than a single processor. I read the recomendations in the manual where is explained what to do to get better performance.

I want to calculate residence time distribution of a system. I used the following lines in the script:

region rtd block 0 0 0 0.01 0 0.01 units box
fix rt all property/atom/tracer region_mark rtd mark_step 1000 marker_style dirac check_mark_every 1000
compute nparticles all nparticles/tracer/region region_count rtd tracer rt
fix extra all print 100 $nparticles file rttd.txt

but this error occurs:
ERROR on proc 0: Substitution for illegal variable (input.cpp:410)

Dear LIGGGHTS users,

I have a simple problem related to dump custom command.
I have defined a per-atom vector which has 12 elements. I perform some calculations on this vector and want to dump it out, however I get the following error.

"Dump custom fix ID does not compute per-atom vector"

This is the input script commands I use:

fix LB all property/atom LB vector yes no no -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1
dump dmp all custom ${nDump} dump.${OutName} id type f_LB[1] ....f_LB[12]

Dear all,

Happy new year 2015 to all members,

To start a new year, I would like to be clarified concerning a solution to convert dump/local output to VTK file. Looking into several discussions in terms of this issue, I am enable to have EVTK and dump2forcenew.py ( or dump2force.py by Mark Bentley) routine however the running come out with error:

File "...LIGGGHTS/mylpp/src/dump2forcenew.py", line 74, in
if forcedata.snaps[fileindex].natoms !=0 and len(forcedata.snaps[0].atoms[0]) != 11:
IndexError: list index out of range

Is LIGGGHTS enable to model the fracture of particles? such as what happens in a ball mill?