How to calculate fabric tensor in Liggghts?

Submitted by jianjianaixuexi on Wed, 09/18/2024 - 13:28

I am a beginner in using LIGGGHTS and I am currently working on calculating the fabric tensor for my simulations. I noticed that LAMMPS has a dedicated compute fabric command for this purpose (https://docs.lammps.org/compute_fabric.html). However, it seems that LIGGGHTS does not have a similar command.

Could anyone please advise on how to calculate the fabric tensor in LIGGGHTS? Are there specific procedures or workarounds available for this?

Thank you in advance for your assistance.

Forums:

deepakpawar.2310 | Wed, 09/18/2024 - 13:46

Hi

Following is the procedure for estimating the fabric tensor:
or you can also refer to the following book, I think chapter 10 for more info!

https://www.taylorfrancis.com/books/mono/10.1201/9781482266498/particula...

Step 1: Obtain coordinate points and radii from the input file (from the dump file)
Step 2: Calculate the contact points from the coordinates and radius of each particle (or you may get from the dump file)
Step 3: Draw normals at the contact points.
Step 4: Calculate the fabric tensor for each contact (loop) by taking the outer product of the normal vectors.
Step 5: Sum the fabric tensors over all the contacts and divide by the number of contacts to get the Global fabric tensor for the ensemble.
Step 6: Calculate the eigenvalues of the global fabric tensor.

Thank you, Happy learning

Deepak K Pawar, IIT Madras