LIGGGHTS® - Developer Forum

Hi. I have used LIGGGHTS to prepare a cube of compressed particles. I need to extract the local contact information such as contact normal, tangential force direction, to construct a four-rank tangent modulus for the granular system.

I am aware of the compute pair/gran/local command but the issue is that I can not use the variable to store the local information that needs further processing. So now I am trying to write my own compute to achieve this goal.

Hello all,
While compiling the src in LIGGGHTS-Public, I am getting the following error.

/usr/bin/ld: warning: libmpi.so.12, needed by /usr/lib/x86_64-linux-gnu//libvtkParallelMPI-6.2.so, not found (try using -rpath or -rpath-link)
size ../lmp_auto

Can anybody please help me with this issue?
Thanks in advance.

Regards,
Tarun

I was wondering if anyone can share the structure of the data file or the actual data file for superquadric particles.

Hi,
In essence I want to create a LIGGGHTS fix for superquadric collision diagnostics. And to do that I would like to access the stored enum that is set in surface_model_superquadric.h which details if particles were in contact last iteration.
This is to avoid doing the intersection check again, as that is both unnecessary to do twice and computationally expensive.

Hello all,
Is the Hertz model given in model same as Hertz Mindlin?

Kindly let me know.

Regards,
Tarun

The issue is that I have ran three different codes keeping everything same but only these 3 commands different in each code

fix gravi all gravity 9.81 vector 0. 0.0 -1.0.
fix p all addforce 0 0 -9.81
fix p all setforce 0 0 -9.81

So, the code with gravity force command acts like the particle comes down very slowly but in their 2 commands i.e. (add-force and setforce) the particles leaves the box quiet early, My question is that in all three cases the particles should act similarly as the force is same in three cases? Is the issue seems to be in fix?

Greetings. I've been working on a hybrid (contact and no contact) force model for LIGGGHTS, which has been done by other users here on the forum before. However, I wish to store a pairwise value that is calculated by surfacesClose so that I can later use it on surfacesIntersect when contact occurs. I've tried creating a new variable on the scdata struct and storing it there, but failed to realize that it is reinitialized every timestep hence this method wont work. Is there any other way I can implement this?

Do we have powder compaction and particle breakage capability in Liggghts?

Hello Team, I'm using fix deform to shear a triclinic periodic cube which is symmetric about origin. Side length of cube in x (say) is -3.5*partDia to 3.5*partDia. Please see attached image t_0.png for initial state, note the coordinate system. I'm using

fix boxDeform all deform 1 xy erate 31 remap v

and everything works fine. In this, we see that the box flips when top corner travels a distance of half the box width as shown in attached image t_t.png in the x-direction.

1. Can we alter this travel distance to a user-defined value, say, quarter of a box length?

hello all,
I was going through the internal codes of Liggghts and found that tag and mask variables are set for each particle. can anybody kindly tell me what are those? As far I understood is the tag is the unique id for each particle and the mask is the processor number in which a particular particle's information is stored. kindly correct me if I am wrong.
thanks in advance.

Best,
Tarun